REF: Upgrade to ironlab 0.16 and remove the figure workarounds

CLAUDE.md

@@ -462,8 +462,7 @@ and `cargo xtask publish <study> [--run <UTC>] [--dry-run]` copies one run's bun
 geometry), pages generated whole by `cargo xtask coverage` (coverage.md), `cargo xtask steps` (branch-tests.md) and
 `generate_subroutine_validation` (subroutines/). Every published number is derived from a fixture directory
 (`tests/fixtures/xfoil/<case>/` or `target/fixtures/<case>/` for `--big` cases) or from `tests/fixtures/subroutines/`.
-Only Markdown, ironlab figures (`.fig`, embedded live in the site) and the branch-coverage study's two SVGs are
-committed under `docs/`. No XFOIL dump, `.dat`, `.pol`, `DUMP`/`CPWR` output or other reference data is ever
+Only Markdown and ironlab figures (`.fig`, embedded live in the site) are committed under `docs/`. No XFOIL dump, `.dat`, `.pol`, `DUMP`/`CPWR` output or other reference data is ever
 committed there — `.gitignore` enforces it — and a table that cannot be regenerated from tracked inputs plus
 `cargo xtask fixtures` is not evidence. The studies: `cargo run -p aerofoil-series` (the validation selection, one
 figure per generator family, the naca456 comparison), `cargo run -p series-cases`, `cargo run -p known-issues`,
@@ -474,11 +473,10 @@ comparison, `studies/study-support/records.rs` — study evidence beside the tes
 user guide's figures (`docs/user-guide/figures/`) are the output of the commands the guide prints, regenerated by
 `scripts/guide-figures.sh`.
 Figures are ironlab figures (`docs/development/conventions/figures.md`), built in Rust by each study from the numbers it
-computes, through `src/output/figures.rs` (colours, ordered-family colours, parameters and labels the ironlab viewer
-filters by, linked axes, validated saving); run folders also hold a PDF of each. The exception is the
-branch-coverage study's branch map and case matrix, still drawn by matplotlib (`studies/branch-coverage/plot.py`
-through `studies/figures/render.sh`, which needs **`uv` installed**) until ironlab has an occupancy-matrix figure
-type. The analysis report (BL-distribution difference tables and
+computes, through `src/output/figures.rs` (colours, ordered-family colours, parameters and tags the ironlab viewer
+filters by, linked axes, saving that refuses a figure which does not validate or lay out); run folders also hold a
+PDF of each. The branch-coverage study's branch map and case matrix are ironlab occupancy and cell figures too. The
+analysis report (BL-distribution difference tables and
 plots for the ±15° N=160 polar) is generated from the `--big` fixture case and is the remaining validation stage.
 
 ## Conventions

Cargo.toml

@@ -27,7 +27,7 @@ env_logger = "0.11"
 
 # Optional figures (behind feature flag): ironlab figure files, pinned exactly because the
 # figure model is still moving between minor versions
-ironlab = { version = "=0.12.0", optional = true }
+ironlab = { version = "=0.16.0", optional = true }
 
 [dev-dependencies]
 approx = "0.5"

docs/development/conventions/figures.md

@@ -7,11 +7,10 @@ icon: lucide/image
 Every yFoil figure is an [ironlab](https://ironlab.org) figure: a file holding the figure's own
 data structure (`.fig`, Protocol Buffers; `.fig.json`, the same model as JSON), not a picture of it. It is opened
 in the ironlab viewer, embedded live in this site, and exported to PDF for publication. The shared conventions
-are implemented once, in `src/output/figures.rs` (feature `plotting`), and every figure is built through it.
-
-The exception is the branch-coverage study's two occupancy figures (`docs/validation/branch-coverage/`): the branch map
-and the case × subroutine matrix are not charts, and stay SVG drawn by matplotlib (`studies/branch-coverage/plot.py`
-through `studies/figures/render.sh`) until ironlab has a figure type for them.
+are implemented once, in `src/output/figures.rs` (feature `plotting`), and every figure is built through it. That
+includes the branch-coverage study's occupancy figures (`docs/validation/branch-coverage/`): the branch map is an
+ironlab occupancy matrix (`ax.occupancy` under `ax.ycategory_groups`) and the case × subroutine matrix is `ax.cells`
+on categorical axes.
 
 ## Who computes what
 
@@ -30,9 +29,9 @@ axis extents. There is no presentation layer that transforms data.
   colourmap for line colours. The family's default or base case is black and drawn on top.
 - **Unordered families of up to four** use `figures::CATEGORY`.
 
-## Parameters and labels
+## Parameters and tags
 
-The viewer sorts, filters and groups figures by their **parameters** (name → value) and **labels** (plain words).
+The viewer sorts, filters and groups figures by their **parameters** (name → value) and **tags** (plain words).
 Every figure carries both, so that all the figures every study produces can be loaded into one viewer and sliced.
 
 **Parameters** say *which* figure this is and *what went in and came out*:
@@ -47,13 +46,26 @@ Every figure carries both, so that all the figures every study produces can be l
 A name that exists as a key in yFoil's own JSON output is spelled exactly as that key. A new value at a place
 is named `<quantity>_<place>_<side>`.
 
-**Labels** are for tags a reader filters on, not for values:
+**Tags** (`fig.tag`) are words a reader filters on, not values:
 
 - the documentation section a figure appears in: `validation`;
 - `xfoil-comparison` for a figure that plots the reference against yFoil;
 - regime tags taken from the inputs: `inviscid`, `compressible` (M > 0), `forced-transition`, `fixed-cl`,
   `low-re` (Re < 1e5).
 
+## Axes
+
+- **Geometry** (an aerofoil section, offsets drawn normal to its surface) is drawn at `Aspect::Equal`, which the
+  layout, the viewer and export all keep. Limits are never widened by hand to fake it.
+- **Pressure coefficient** is plotted as \(C_p\) on a reversed axis (`yreverse(true)`), suction up, never as
+  \(-C_p\).
+- **Rows of names** (cases, subroutines) are categorical axes (`ycategories`, first at the top), set in monospace
+  with `\texttt{…}` (escape `_`).
+- **Reference lines** (a tolerance, interval ends) are `hline` / `vline`, which span the axes at any zoom.
+- **Non-finite values** are marked by `Marker::VLine` ticks at the top edge, at data x and axes-fraction y with
+  clipping off, so they stay at the edge while the axes autoscale, pan and zoom.
+- **Stacks sharing x** show x tick labels on the bottom row only (`xtick_labels_hidden()` above).
+
 ## Linked axes
 
 Panels that share an independent variable (α, x/c) have that axis linked across the whole figure. Panels that plot
@@ -62,14 +74,22 @@ dependent axis linked too. Two axes with different quantities are never linked,
 
 ## Legends
 
-Where a figure has one key for many panels, the legend goes in a **panel legend** (`fig.panel_legend(row, col)` +
-`ax.legend_in(key)`) in a tile of its own. This replaces the hand-placed legend strips of the matplotlib figures.
+Where a figure has one key for many panels, the legend goes in a **panel legend** (`fig.panel(row, col).legend()` +
+`ax.legend_in(key)`) in a tile of its own, whose row is sized to it (`fit_row`), never by a calibrated weight.
 A legend that belongs to one panel stays in that panel.
 
+- **A reference and its variants**: the default section or base case is drawn last, so it is on top, and listed
+  first, on a row of its own (`full_row`), the members after it in order.
+- **Meanings shared by many artists** (a marker shape for a kind of point, a colour for a side) are explained once by
+  `custom_item` entries, in a key of their own if the figure also names curves, never by dummy artists or one entry
+  per combination.
+- Columns are `LegendEntryColumns::Auto` or a fixed count, never chosen by trial export.
+
 ## Saving
 
-- `figures::save(fig, path)` validates the figure and refuses to write one with validation errors. The encoding
-  follows the extension.
+- `figures::save(fig, path)` validates the figure and refuses to write one with validation errors, or whose layout
+  (`Figure::layout_warnings`) overflows a legend, clashes two legend entries or puts text beyond the page. The
+  encoding follows the extension.
 - `figures::save_with_pdf(fig, stem)` also writes the PDF, for the run folders' LaTeX reports.
 - Study run folders hold `.fig` and `.pdf`. The documentation holds `.fig` only.
 - The user guide's figures (`docs/user-guide/figures/`) are the output of the very commands the guide prints, run by

docs/development/testing/README.md

@@ -18,10 +18,8 @@ measure the reference and compare whole runs, and add nothing the tests rely on.
 
 Figures are [ironlab](https://ironlab.org) figures, built in Rust by each study from the numbers it
 computes (`docs/development/conventions/figures.md`). They are embedded live in these pages: pan, zoom and toggle lines from the
-legend. Each carries parameters (case, conditions, outputs) and labels, so every study's figures can be loaded
-together into the ironlab viewer and sorted, filtered and grouped. A study's run folder also holds a PDF of each. The branch-coverage study's branch map and case matrix are the exception: they are SVGs drawn by
-matplotlib (`studies/branch-coverage/plot.py` through `studies/figures/render.sh`, which needs
-[`uv`](https://docs.astral.sh/uv/) installed).
+legend. Each carries parameters (case, conditions, outputs) and tags, so every study's figures can be loaded
+together into the ironlab viewer and sorted, filtered and grouped. A study's run folder also holds a PDF of each.
 
 | Page | What it shows | Regenerate with |
 |---|---|---|

docs/user-guide/commands/plotting.md

@@ -19,7 +19,7 @@ Open a figure in the ironlab viewer, a desktop application that pans, zooms, rea
 the curves and hides series from the key:
 
 ``` sh
-cargo install ironlab-viewer --version 0.12.0
+cargo install ironlab-viewer --version 0.16.0
 ironlab-viewer naca0012.fig
 ironlab-viewer *.fig           # several: the figure browser lists them
 ```
@@ -65,12 +65,11 @@ yfoil plot analysis a5.json                              # writes a5.fig
 
 For the NACA 4412 at α = 5°, Re = 10⁶:
 
-<ironlab-figure src="../figures/a5.fig" format="fig" name="a5" alt="NACA 4412 at alpha 5 degrees, Re 1e6: -Cp and Ue over x/c, upper and lower surfaces, above the aerofoil outline">NACA 4412 at alpha 5 degrees, Re 1e6: -Cp and Ue over x/c, upper and lower surfaces, above the aerofoil outline</ironlab-figure>
+<ironlab-figure src="../figures/a5.fig" format="fig" name="a5" alt="NACA 4412 at alpha 5 degrees, Re 1e6: Cp and Ue over x/c, upper and lower surfaces, above the aerofoil outline">NACA 4412 at alpha 5 degrees, Re 1e6: Cp and Ue over x/c, upper and lower surfaces, above the aerofoil outline</ironlab-figure>
 
-\(-C_p\) and \(U_e/U_\infty\) over \(x/c\) from a single-point analysis, upper surface
+\(C_p\) and \(U_e/U_\infty\) over \(x/c\) from a single-point analysis, upper surface
 blue and lower red, above a strip with the aerofoil outline; the three share a linked
-\(x\) axis. \(C_p\) is plotted negated, with suction up, because ironlab has no reversed
-axis. A point whose numbers were withheld (an invalid point analysed without
+\(x\) axis. The \(C_p\) axis is reversed, so suction is up. A point whose numbers were withheld (an invalid point analysed without
 `--allow-invalid`) has no distributions to draw, and is refused.
 
 ## The `plot foil` command { #foil }
@@ -110,6 +109,7 @@ polar JSON written with `--distributions` (one design point per α).
 Each quantity gets its own hue and its own scale; each design point gets a tone
 and dash pattern, so several angles overlay legibly. The markers are open shapes, one per
 kind (○ stagnation, □ transition, ◇ forced transition, △ separation, ▽ reattachment),
-yellow on the upper surface and green on the lower, and the key below the axes names each
-kind and side drawn. The axes are scaled equally in \(x\) and \(y\) at the figure's own
-size, so the section is undistorted; zooming in the viewer changes the two independently.
+yellow on the upper surface and green on the lower. Below the axes are two keys: the curves,
+and the markers, which explain each shape drawn once in grey and each side's colour once.
+The axes are kept at equal aspect, in the viewer while panning and zooming too, so the
+section and the offsets normal to it are undistorted.

docs/user-guide/get-started/install.md

@@ -30,7 +30,7 @@ Plotting is behind a cargo feature; build with it enabled if you want
 
 ``` sh
 cargo install --path . --features plotting
-cargo install ironlab-viewer --version 0.12.0
+cargo install ironlab-viewer --version 0.16.0
 ```
 
 ## Check it works