docs: add Ida Faber blendshape dialogue note

docs/design/56-focused-npc-dialogue-portrait-lipsync-design.md

@@ -167,9 +167,42 @@ blendshape and bone effectors. It also supports preset or custom effector lists.
 This matches our tier 3 direction, but it should remain behind the isolated
 Convai import lane and not be required for the first focused dialogue UI pass.
 
+Ida Faber's blendshape documentation is especially relevant for semi-real
+candidate bodies. It documents Apple ARKit 52 blendshapes, facial capture, and
+body customization morphs, which makes Ida-compatible bodies plausible targets
+for an ARKit-style lip sync profile. The implementation should still inspect
+the actual imported Unity mesh before assuming every purchased Ida character has
+the same available blendshape names.
+
 Reference:
 
 - [Convai Unity: Adding Lip-Sync to your Character](https://docs.convai.com/api-docs/plugins-and-integrations/unity-plugin/adding-lip-sync-to-your-character)
+- [Ida Faber Docs: Blendshapes and Facial Animation](https://docs.idafaber3d.com/features/blendshapes)
+
+### Ida Faber ARKit Blendshape Lane
+
+Use this lane only for Ida-family bodies whose imported Unity meshes expose the
+needed face blendshapes.
+
+Implementation rules:
+
+- Add an `IdaFaberArkit52` lip sync profile only after inspecting the real
+  imported `SkinnedMeshRenderer` blendshape names.
+- Start with a minimal mouth set for alpha: `jawOpen`, mouth close or funnel
+  shapes if present, and optional blink shapes.
+- Keep the text-timed fallback available for any Ida body missing compatible
+  facial targets.
+- Do not drive full expression changes from dialogue text without authored
+  emotion rules. Mouth motion and blink are enough for the first pass.
+- Treat ARKit blendshape weights as local presentation data only.
+
+Evidence:
+
+- Screenshot or inspector note listing the focused Ida body face mesh and its
+  available mouth/blink blendshape names.
+- Play Mode capture showing text-timed or audio-driven mouth movement on one
+  compatible Ida body.
+- Fallback note for one body or prefab without compatible face blendshapes.
 
 ---
 
@@ -294,6 +327,8 @@ Build:
 - Do not require Convai to be imported for D1 or D2.
 - When Convai is imported later, map compatible bodies through a
   character-specific lip sync profile instead of one global face assumption.
+- For Ida-family bodies, validate the real Unity blendshape list first and use
+  an ARKit-style profile only when the imported mesh supports it.
 
 Evidence:
 
@@ -355,4 +390,3 @@ Do not cut:
 - speaking-state cleanup on exit or failure
 - server-authority boundary
 - readable focused dialogue layout
-