docs: update mesh, viewers, and selection decisions

Document the separated front/back/walls extrusion, material-level back
flips, CardID sprite selection from the parent deck, index-path tree
selection, and the Bounds-inside-Suspense camera fit.

docs/architecture.md

@@ -52,8 +52,8 @@ apps/web ──► apps/proxy ──► packages/tts ──► packages/shared
   (image → vector shape) over HTTP.
 - **`apps/web` → `packages/extract`** — uses `buildTree` / `collectRefs`
   to analyze a loaded `TTSMod` in the browser (tree sidebar + asset refs).
-- **`apps/web` → `packages/mesh`** — extrudes 2D shapes into 3D geometry for
-  the tile and token viewers.
+- **`apps/web` → `packages/mesh`** — extrudes 2D shapes into 3D geometry
+  (`{ front, back, walls }`) for the tile, token, and card viewers.
 - **`apps/proxy` → `packages/tts`** — calls `fetchMod` / `getFileName` to serve
   item requests.
 - **`apps/proxy` → `packages/shared`** — uses shared types and zod schemas for
@@ -93,7 +93,7 @@ apps/web ──► apps/proxy ──► packages/tts ──► packages/shared
 | `zod`              | Runtime validation                        | `apps/proxy`, `packages/shared` |
 | `three`            | 3D rendering                              | `apps/web`         |
 | `@react-three/fiber` | React renderer for three.js             | `apps/web`         |
-| `@react-three/drei`  | three.js helpers (controls, textures)   | `apps/web`         |
+| `@react-three/drei`  | three.js helpers (controls, textures, bounds) | `apps/web`   |
 | `@react-three/postprocessing` | Post-processing effects    | `apps/web`         |
 
 ### Runtime constraints