Anim: Slice A — Morph targets / blend shapes (import, preview, edit, export)

[fernandotonon]

Parent epic: #517

Goal

First-class support for morph targets / blend shapes — the per-vertex deltas that drive facial animation and character expressions. Authors create / edit weights, preview, and round-trip through FBX and glTF.

Why

Every modern game engine consumes blend shapes. QtMeshEditor currently drops them on import — there is no MorphAnimationTrack or Pose usage in src/. Users can't author or even preview facial animation today.

Scope

• Importer: extend MeshImporterExporter to detect FBX blend shapes and glTF morph targets. Convert to Ogre::Pose + Ogre::MorphAnimationTrack (Ogre 14.5 supports both — we just don't use them).
• MorphAnimationManager singleton (src/MorphAnimationManager.{h,cpp}) — owns per-entity morph state, emits morphTargetsChanged, morphWeightChanged.
• Inspector "Morph Targets" section under Animation Mode:
  • List of named morph targets with weight sliders (0–1, optionally -1..1 for "shape minus base").
  • Search/filter by name (characters often have 50+ targets).
  • Multi-edit: select multiple targets and apply a common value.
  • Reset all / lock targets.
• Dope sheet integration: morph-weight tracks appear in the dope sheet alongside bone tracks; keyframable on the slider.
• Curve editor integration: morph weight curves edit just like bone TRS curves.
• Authoring (basic v1):
  • Save the current edit-mode vertex positions as a new morph target relative to the base mesh.
  • Rename / delete morph targets.
  • Live preview: scrubbing weights updates the mesh in-viewport.
• Exporter: FBX (existing FBXExporter) and glTF write morph targets.
• CLI: qtmesh morph model.fbx --list [--json], qtmesh morph model.fbx --set <name>=<weight> -o out.fbx.
• MCP: list_morph_targets, set_morph_weight, add_morph_target, delete_morph_target.

Acceptance Criteria

• Importing an FBX or glTF with blend shapes produces visible, named morph targets the user can preview.
• Weight sliders update the mesh in real time.
• Dope sheet and curve editor show and edit morph-weight tracks.
• User can author a new morph target from an edit-mode mesh delta.
• Export round-trip preserves all morph targets and their animation tracks for at least FBX and glTF.
• All operations are undoable.
• Headless-CI-safe unit tests cover import, weight set, and round-trip.
• Sentry breadcrumbs scene.anim.morph.* recorded.

Effort

~10 days.