Align NPC voice lane with Ida Faber pipeline

[JOY (JOY)]

Summary

• Correct the NPC voice and dialogue source of truth away from Convai and toward the custom SECOND SPAWN pipeline.
• Align AGENTS.md and .claude/CLAUDE.md with custom api.dos.ai dialogue, scoped voice sessions, and Ida Faber retargeting/blendshape readiness.
• Update project docs, ADR references, setup notes, and GitHub tracking text so Import Ida Faber character packs in an isolated Unity pass #25 and Track NPC voice session and custom Ida Faber facial-animation lane #262 point at Ida Faber/custom facial animation instead of Convai.

Notes

• The repo now only mentions Convai as a negative guard: do not use it as a phase 1 dialogue dependency.
• GitHub issues Import Ida Faber character packs in an isolated Unity pass #25 and Track NPC voice session and custom Ida Faber facial-animation lane #262 were renamed and rewritten to match the Ida Faber/custom lane.

Verification

• npx.cmd --yes markdownlint-cli2 README.md ROADMAP.md CHANGELOG.md CONTRIBUTING.md SECURITY.md AGENTS.md .claude/CLAUDE.md "docs/**/*.md" - passed.
• git diff --check - passed.
• AGENTS.md and .claude/CLAUDE.md sister-file sync check - passed.
• Local review fallback - docs-only/context correction, no gameplay authority changes, no provider keys added, Unity compile not required because only a C# comment changed.