Desktop ergonomics: zoom, panel resize, motion bar, exporter tagging

[OmarB97]

Summary

Ports a set of desktop ergonomics fixes into real source. These were previously applied to the built app as post-hoc patches against the extracted AppImage; every one of them is now a normal source change, so a future app update no longer silently erases them. Builds on top of #242 (animated model playback) and #243 (Library thumbnails and resize), both merged in unchanged.

What changed

• Window zoom: Ctrl/Cmd with + / - / 0 scales the whole window like a browser, clamped to [-2, 4] and persisted to <userData>/ui-zoom.json. Implemented in the main process against webContents.setZoomLevel, not CSS zoom, because a CSS transform does not tell the 3D viewport it happened, and pointer math there (raycasting, gizmo dragging) then reads wrong coordinates.
• Generate panel resize: the handle was a 1px, resting-invisible strip capped at 520px. It is now 2px with a visible resting tint plus a stronger hover/active highlight, marked up as a real separator (role, aria-orientation, title), capped at 900px, and its width persists to localStorage the same way the Library panel already does.
• Parameter labels: the label column truncated anything longer than a couple of words. Widened and now wraps instead of clipping.
• Prompt textarea: 14 rows by default (was 3) and user-resizable (resize-y, 14rem min-height); was resize-none.
• Section headings: the image input reads "Your sketch or photo — required" and the text input reads "Extra details — optional", instead of the unlabeled "Image" / "Text".
• Motion bar: the clip picker was a raw DOM <select> injected at the model origin, hard-cutting between clips by tearing down and recreating the whole AnimationMixer. Rebuilt as a real React overlay (bottom-left, matching the existing toolbar/stats-overlay pattern): the mixer now lives for as long as the model does, clip switches cross-fade over 0.25s, and the clip list is reported up to the viewer the same way mesh stats already are. Zero clips renders nothing, one clip shows its name read-only, more than one gets a dropdown plus a "Next" button. All playback loops.
• Exporter naming, grouping, and tagging: the built-in mesh-exporter gains model_name, project, and tags params. Files land at <Exports>/<project-slug>/<name-slug>-<4-char-unique>.<ext>, falling back to a dated name when unnamed. Tags are what the operator typed plus what the file itself can tell (rigged, animated + clip-<name> per clip, textured, a poly-count tier, the project slug), written both as a <file>.tags.json sidecar and embedded under extras.modly in the glTF itself. Ported from the already-working implementation running on the operator's machine, not reinvented.
• New: tag suggestion pills: the tags field in the Generate form now shows clickable suggestion pills underneath it — slugified words from that node's typed name/project fields, plus a small fixed game-asset vocabulary (prop, character, creature, environment, weapon, furniture, hero-asset, background, low-poly, stylized, realistic), deduped and capped at 10. Clicking toggles the tag in the comma-separated value. Fully client-side, no network calls.
• Added a text param type (distinct from string, which renders a folder picker) so free-text fields like the exporter's new ones render as plain inputs instead of falling through to a numeric one.

Test plan

• npm install && npm run build — clean, no errors.
• npm run lint — 0 problems.
• npm test — 23/23 Python tests, 40/40 Node tests, all passing.
• Packaged with npm run package (electron-builder, AppImage target) and installed as the actual app the operator launches daily, replacing the previous extracted build (backed up first).
• Verified on the real desktop, not just from logs:
  • Zoomed in/out with Ctrl/Cmd +/-/0; UI visibly scaled and ui-zoom.json updated on disk each time.
  • Dragged the generate panel wider; restarted the app; width was still there.
  • Dragged the Library panel wider (pre-existing Add Library thumbnail previews and a resizable panel #243 behavior); still works after the merge.
  • Library rows show real .thumb.png thumbnail images, not placeholders.
  • Opened a two-clip rigged model (squid-seamless-loop.glb); motion bar showed a dropdown with both clip names (idle_breathe, startle_flick) and a Next button; clicking Next cycled and cross-faded between them, then wrapped back around.
  • Export section shows the three new fields as working text inputs, plus the tag suggestion pills underneath the tags field, capped at 10 as designed.

Risk / rollback

All changes are additive to existing components; nothing upstream of these files changes behavior for models/flows that do not touch them. The riskiest piece is the motion bar rewrite (GltfMeshModel in Viewer3D.tsx) since it replaces the mixer lifecycle from #242 rather than only extending it — verified above with a real two-clip model, including the cross-fade and wraparound. If something regresses, reverting this branch on top of #242+#243 restores the prior (single mixer teardown per clip, DOM <select>) behavior.

Notes for reviewers

• Play animation clips in the 3D viewer #242, Add Library thumbnail previews and a resizable panel #243, and Normalize object-shaped manifest inputs in the workflow preflight check #244 are untouched by this branch (Normalize object-shaped manifest inputs in the workflow preflight check #244 is on an unrelated branch and was never merged in here).
• The text param type is new to the codebase (no other manifest currently declares it); it is additive to the existing ParamSchema union and only changes rendering for nodes that opt into it.
• Package-lock.json is included because npm ci currently fails against package.json on main (stale lockfile); npm install — what upstream CI already falls back to — regenerated it.