docs(architecture): update CLAUDE.md, project structure, D-170 for implant UI system

- CLAUDE.md: added Implant UI component library section (D-169, D-170)
- project-structure.md: added client/ui/implant/, hud_groups.gd, gameplay_renderer.gd
- D-170: corrected implementation note from visibility toggling to z-index layering

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

.claude/rules/project-structure.md

@@ -2,6 +2,14 @@
 
 ```
 client/               # Godot 4 client
+  ui/
+    implant/          # Implant UI component library (D-169): ImplantPanel, ImplantHeader,
+                      #   ImplantSeparator, ImplantDataRow, ImplantTextBlock, default_implant.tres
+  scripts/
+    autoloads/
+      hud_groups.gd   # HUD z-index layer manager (D-170): GAMEPLAY/INSERT/FULLSCREEN/MODAL modes
+    rendering/
+      gameplay_renderer.gd  # Base class for occludable renderers; connects to HudGroups signal
 server/               # Rust/bevy_ecs simulation server
 tooling/              # Build tools, scripts, asset pipelines
 tests/                # Integration and end-to-end tests