Track NPC voice session and custom Ida Faber facial-animation lane

[JOY]

Purpose

Track the future NPC voice lane without committing to broad voice integration too early.

Scope

• Nakama RPC for short-lived api.dos.ai voice/session material.
• Unity playback through scoped sessions only, with no provider keys in the client.
• Custom voice and facial-animation lane owned by SECOND SPAWN, not Convai.
• Ida Faber-compatible facial animation through verified Unity Humanoid retargeting and imported SkinnedMeshRenderer blendshape names.
• Higher-quality NPC voice and interruption only after cost, latency, reliability, and stable voice identity are acceptable.
• Future audio-amplitude or provider viseme/blendshape lip sync hooks after Add focused NPC portrait and speaking animation to dialogue UI #139 ships the text-first portrait and speaking-animation slice.

References

• docs/design/56-focused-npc-dialogue-portrait-lipsync-design.md
• docs/design/28-character-body-and-roster-design.md
• docs/design/37-ai-npc-backend-client-roadmap.md
• Ida Faber Unity retargeting: https://docs.idafaber3d.com/unity/retargeting
• Ida Faber blendshapes and facial animation: https://docs.idafaber3d.com/features/blendshapes

Notes

Text-first NPC behavior remains the default until the core AI NPC loop is stable. Voice, TTS, Ida Faber blendshape mapping, and viseme lip sync should not block the first focused dialogue portrait implementation.

[JOY]

Implemented in #270 and merged into dev.

Summary:

• Added the disabled-by-default secondspawn_voice_session_request Nakama RPC for scoped api.dos.ai voice playback sessions.
• Wired Unity gateway DTOs and prototype NPC chat hotkey through Nakama only.
• Documented the text-first voice lane and Convai as an isolated future spike, not a blocker.

Verification:

• Local npm.cmd run build passed.
• Local npm.cmd test passed.
• CI nakama build + test passed.
• CI markdown-lint passed.
• Local code-review fallback approved.

Known environment blocker: Unity batchmode still stops before script compile because Package Manager fails with The "path" argument must be of type string. Received undefined. No packages loaded.