Say "rewritten" instead of highlighting the whole plan

[HamptonMakes]

The "changed since you last looked" highlights were making plan pages look messy, and there were two separate reasons.

Saturation

The diff was correct; the message was worthless. Open a plan while an agent is still drafting it (the presence channel records the visit), or come back after a rewrite, and every section differs from your baseline — so every section lit up. "Everything changed" is what a reader already assumes on a v5 plan they half-saw once.

Plans::ChangedSections now returns a small result (keys + rewritten?) instead of a bare array, and reports a rewrite when most of the document is new. "Most" is measured two ways — more than half the sections and more than half the text — because either measure alone misreads a common shape: a swarm of one-line sections changing isn't a rewrite, and neither is one long section of ten getting edited. It only applies to documents of four or more sections; below that, banding the whole thing is a few inches of tint, which is legible and more useful than a sentence about it.

In that case the page drops the highlights entirely and carries one line above the content: "Rewritten since you last looked. See what changed", linking to the plan's history.

The two thresholds are REWRITE_RATIO and REWRITE_MIN_SECTIONS in the service, easy to move once we've seen this on real plans.

The barcode

Independent bug in the same feature. The Stimulus controller added .section-changed to each top-level block, and the CSS gave each one its own tinted, rounded, left-barred box — so a single changed section of six paragraphs rendered as six stripes with untinted gutters between them and a broken-up accent bar. It looked messy even when only one section had changed.

Adjacent changed blocks are now grouped into runs (--start / --end markers), and within a run the inter-block margins become padding inside the tint. A run reads as one continuous band with one unbroken bar, rounded at the ends only. Mid-run headings keep their breathing room as padding inside the band rather than a gap through it. The band CSS is scoped under .markdown-rendered so it outranks the per-element markdown margins.

Wrapping the run in a container div would have been simpler, but reference_preview_controller#renderSection walks heading.nextElementSibling to build section previews, so the flat structure has to stay.

Screenshots

Real page, dark mode, 2×. Each pair is the same plan and the same content, with and without this change.

The rewrite case — you glanced at the plan while it was still a stub, then the agent wrote the whole thing.

Before	After

Every one of the nine sections bands, and the page says nothing. After: one line above the title — "Rewritten since you last looked. See what changed" — and a clean document.

Two genuinely changed sections — "How it works" and "Themes", adjacent.

Before	After

Before: four separate boxes with untinted gutters and four disconnected bar segments for one continuous stretch of changed text. After: one band, one bar, rounded at the ends only, with the mid-run "Themes" heading keeping its breathing room inside the tint.

Reviewer notes

• ChangedSections.call changed return type (array → Result). Only PlansController#show and show.html.erb consume it; NONE is the empty result for the "first visit / nothing new" paths.
• Highlights remain strictly once-only and per-viewer: the same request advances last_seen_at. Worth knowing while testing — PlanPresenceChannel#ping also advances it while a plan page sits open, so a tab left on the plan will eat the highlight before you can reload.
• 1726 specs pass; RuboCop clean. New coverage for the rewrite threshold and the rename discount in spec/services/plans/changed_sections_spec.rb, and the data attributes in spec/requests/changed_sections_highlight_spec.rb.
• Second commit addresses Codex's rename finding: a renamed heading files an untouched body under a new slug key, which the key-level diff can't tell from new text, so a batch of renames could claim a rewrite. Bodies that already existed somewhere in the old document are now carried over, matched one for one, and don't count toward "most of this is new" — they still highlight.
• Unrelated to this feature, riding along in the second commit: voice_commenting_spec.rb failed test-postgres here, the third flake from that file across two PRs. The cause is a race, not load — the mic control is server-rendered but inert until its Stimulus controller connects, so an example that pressed the key first went nowhere. Neither the button nor its tooltip is a usable readiness signal, so voice_controller#connect now sets data-voice-ready and every visit in that spec waits for it. That's a one-line app change made for testability, in a PR about highlights — flagging it rather than folding it in quietly. 20/20 locally, three runs, and test-postgres is green.
• Verified visually against the real page in both states — a full A/B on identical content, with and without the change — plus a DOM geometry check confirming every adjacent pair in a run measures a 0.00px gap, including paragraph→heading and paragraph→code block.

🤖 Generated with Claude Code

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