feat(anim): idle and walk clips on the MPFB rig

Two parametric cycles authored at 30 fps instead of hand-keyed poses, so the loop
closes by construction: GigLine_Idle (60 f, breathing sway, feet planted) and
GigLine_Walk (30 f, one stride, hip 0.45 rad / knee 0.55 / arm 0.32, arms
counter-phased, torso counter-rotation).

The limb axes were measured, not assumed: a probe rotated upperleg01.L by 0.5 rad
on each axis and read foot.L, which moved -0.022 -> +0.362 in Y on X, twisted on Y
and abducted on Z. Using the wrong axis here would have produced a character
scissoring sideways, which no import error would have caught.

The character export preset now bakes animation. Without bake_anim the exporter
writes a static bind pose and Unreal imports a mesh with no AnimSequence and no
error, so the importer asserts a clip exists and prints VERDICT: PASS/FAIL.

Verified in /Game/Test/Character: Idle 1.967 s and Walk 0.967 s, both AnimSequences,
skeleton intact. Playback on a possessed pawn is not yet verified: the demo pawn has
no visible body, so that check belongs with the third-person camera item.

Docs/Architecture/05_building_block_view.md

@@ -56,6 +56,7 @@ Python scripts in `Tools/` drive the content pipeline:
 | --- | --- |
 | `export_*`, `hero_facade_build` | Blender headless export (FBX) |
 | `ue_import_*`, `ue_hero_facade_import` | Unreal headless import + placement |
+| `character_anim_build`, `ue_character_anim_import` | Character animation clips (`GigLine_Idle`, `GigLine_Walk`) and their import |
 | `ue_build_demo_map`, `ue_build_review_map` | Map assembly (lighting, meshes, player start) |
 | `ue_create_input_assets` | Enhanced Input actions + mapping context |
 | `render_screenshots.sh` | Screenshot capture pipeline |

Docs/Architecture/architecture.md

@@ -200,6 +200,7 @@ Python scripts in `Tools/` drive the content pipeline:
 | --- | --- |
 | `export_*`, `hero_facade_build` | Blender headless export (FBX) |
 | `ue_import_*`, `ue_hero_facade_import` | Unreal headless import + placement |
+| `character_anim_build`, `ue_character_anim_import` | Character animation clips (`GigLine_Idle`, `GigLine_Walk`) and their import |
 | `ue_build_demo_map`, `ue_build_review_map` | Map assembly (lighting, meshes, player start) |
 | `ue_create_input_assets` | Enhanced Input actions + mapping context |
 | `render_screenshots.sh` | Screenshot capture pipeline |