feat(client): character creation screen with live 3D preview (#705)

Full character creation UI with 5-tab customisation panel (Body, Head,
Hair, Clothing, Accessories), live 3D compositor preview via SubViewport,
D-165 color picker modal, keyboard navigation, and game flow integration.

- CharacterCreation scene + script (~1440 lines) implementing wireframe spec
- SubViewport with Camera3D (frontal/dramatic/overhead presets per D-158)
- Cardinal rotation (Q/E) per D-155, randomise (R), Tab/Enter/Esc navigation
- Body type grid (11 types, D-159), skin tone dock (9 tones, shared state)
- Head template, hair, facial hair, eyebrow grids with DirAccess asset scanning
- Clothing slot selector with per-item Primary/Secondary/Accent tints
- Accessory slot selector with Primary/Secondary tints (Array[Color] descriptor)
- 54-swatch color picker modal (D-165) with hex input and recent colors
- Auto-derive flags for highlight, eyebrow tint, facial hair tint from hair primary
- Game flow: main_menu → archetype select → character creation → game start
- GameState.character_visual_descriptor field for gameplay consumption
- Updated accessory_tints from single Color to Array[Color] in descriptor + compositor
- 40+ GdUnit tests covering scene structure, signals, keyboard nav, color derivation

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

client/data/ui-strings.yaml

@@ -218,3 +218,11 @@ character_select:
   detective_card_name: "Detective"
   detective_card_role: "Commission investigator — External assignment"
   detective_card_tone: "Institutional authority. Analytical lattice. You were sent here."
+
+character_creation:
+  btn_back: "[ESC] Back"
+  btn_randomise: "[R] Randomise"
+  btn_start: "[ENTER] Start"
+  btn_rotate_left: "[Q] ◄"
+  btn_rotate_right: "► [E]"
+  search_placeholder: "Search…"