feat(runtime): strengthen hooks, channels, embeddings, and audio

[itsddvn]

Summary

• preserve Feishu group context and wire database-backed writer stores
• add script-hook context injection, UI/config support, documentation, and prompt provider/model selection
• recover and backfill missing embeddings safely
• resolve TTS voice/model per actual tenant/global fallback provider
• make OpenAI-compatible STT honor configured timeout while preserving per-call override
• merge current upstream/dev (c1fb4125) into the branch

Risk review

• independent review found no Critical/High blockers
• one Medium TTS deep-fallback issue was found, fixed, regression-tested, and re-reviewed with no remaining findings
• no new tenant-isolation, API, race, error-handling, or security issue evidenced

Verification

• go build ./...
• go build -tags sqliteonly ./...
• go vet ./...
• go test ./...
• go test -race -count=1 ./internal/audio ./internal/audio/openaicompat ./internal/tools
• TEST_DATABASE_URL=... go test -race -tags integration ./tests/integration/
• cd ui/web && pnpm install --frozen-lockfile && pnpm build
• runtime probes: tenant TTS routing, deep fallback provider options, STT configured timeout, STT per-call override
• git diff --check

Surface parity

• Gateway/backend: updated and verified
• API contract: N/A; no request/response wire shape changed
• Web UI: hook configuration changes included and production build passes
• CLI/runtime: gateway setup/context wiring changes included
• Desktop: no desktop-specific UI contract changed; SQLite build passes

Notes

• existing local untracked files were intentionally excluded from this PR.

[clark-cant]

Reviewed metadata, diff scope, duplicate search, project context, and green CI. Approving for merge.