fix(snippets): export Y-up, meter glTF for Godot and Unreal too

[TMHSDigital]

Closes #346.

Problem

• Godot preset: exported Z-up glTF (export_yup=False). The glTF 2.0 spec fixes +Y up and meters, and Godot is right-handed Y-up and imports glTF per the spec. So every Godot asset exported this way arrived rotated −90° about X. The skill's only justification was that matching Unity would make "the axis contract untestable".
• Unreal glTF preset: baked 100x. Unreal's Interchange glTF importer already converts meters to centimeters (import_scale, default 100), so a baked file imports 100x too large.

Sources:

• Unreal GLTFImportOptions.import_scale ("default 100 … meters (glTF) to centimeters (Unreal)")
• Godot docs, importing 3D scenes / export considerations (Y-up; export glTF with +Y Up on)
• Godot docs, node type customization (import-hint suffixes)

Change

• snippets/export_preset_godot.py: export_yup=True. The header explains Godot's real per-engine lever: node-name hints such as -convcolonly.
• snippets/export_preset_unreal.py: the glTF function drops the 100x location/scale bake and exports meters, Y-up. The FBX function (axis_forward/axis_up/global_scale=100) is unchanged.
• skills/engine-export-presets:
  • a new "glTF is the same for every engine" section;
  • Godot and Unreal sections rewritten;
  • common mistakes 4–6 replaced: Z-up for any engine, baking 100x into Unreal glTF, using axes to express engine differences.
• Pipeline template: export_preset() is now one spec-compliant call for every --preset, kept as the hook for engine import hints. The README drops the "Unreal mutates selected meshes" pitfall, which no longer applies.
• examples/export-preset-axis: same mesh, checks, exit codes, falsifier and still. The second export is now named for what it is (a naive export_yup=False file, which is what any glTF engine would show), not "Godot":
  • identifiers renamed unity_*→preset_* and godot_*→zup_*;
  • the README explains the history;
  • gallery.json teaches/alt/witness text updated, gallery regenerated.
• Text in the rule, CLAUDE.md skills table and ROADMAP line: corrected.

Evidence

Proven by live run (--factory-startup; binaries report 5.2.1 LTS and 4.5.11 LTS). Results were identical on both versions.

Run	Result
Each preset snippet exports a 0.2×0.2×2 m post, re-imported (Blender's importer reads Y-up like the engines)	godot / unreal / unity: span [0.2, 0.2, 2.0], standing. The old Unreal bake would give [20, 20, 200]; the old Godot preset would lie
export_preset_axis.py check	exit 0. preset_reimport z=0..2.46 (standing), zup_reimport y=-2.46..0 (lying), tip_err 2.4e-07
export_preset_axis.py --same-axis (catalog falsifier)	exit 9, unchanged
Pipeline template --preset godot / --preset unreal on the CI fixture	exit 0 / exit 0
Render path --output --engine cycles (5.2.1)	exit 0. Framing fill 0.794, margins ≥ 0.034; asset-quality gate passed; gizmo fit_err=0. The image has no text, so the committed hero is unchanged (the rename touches identifiers and gizmo object names only)

Validators: check_frontmatter, check_skill_refs, check_counts, check_import_export_rules, check_exit_code_readme, check_smoke_catalog, check_engine_id, check_render_gates and check_site_links (135 pages, 0 failures) pass. build_claude_rules --check is clean.

Generated HTML read: the card and detail alt text in docs/gallery/index.html and docs/gallery/export-preset-axis/index.html carry the new wording.

Not done: an engine-side import test (Godot or Unreal are not available here). The Unreal behaviour rests on Epic's documented import_scale default.

🤖 Generated with Claude Code

[TMHSDigital]

CI evidence before merge: all checks pass ( 13 pass ). Blender Smoke on PR head: Blender 5.2.2 LTS / Blender 4.5.14 LTS. Summaries (happy path; falsifiers) per leg: 141 passed, 3 skipped, 0 failed;136 passed, 6 skipped, 0 failed;143 passed, 1 skipped, 0 failed;142 passed, 0 skipped, 0 failed;