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/scripts/autoloads/game_state.gd

@@ -97,6 +97,11 @@ var pending_load_path: String = ""
 # Default: "detective" — fallback for legacy saves without character.txt.
 var character_archetype: String = "detective"
 
+# #705: Character visual descriptor — set by character_creation.gd on confirmation.
+# Passed to EntityRenderer for the player entity's CharacterVisual on game start.
+# Null when no custom appearance has been selected (fallback: default descriptor).
+var character_visual_descriptor: CharacterVisualDescriptor = null
+
 # #646: AI-Enhanced Dialogue enabled state (D-138).
 # Runtime toggle — true means the LLM re-voicing pipeline should run (server-side).
 # Default: true (opt-out model per D-138 §8). Hardware detector may disable at startup