merge: integrate origin/main (406 commits) into live branch

Merge upstream's paired-room stabilization, dedicated message-runtime-loop,
outbound delivery refactor (ipc-outbound-delivery / deliverFormattedCanonicalMessage),
discord module split, dashboard rework, and migrations 015-018 into our branch.

Conflict policy: prefer upstream for the heavily-refactored paired-room /
message-runtime / db cluster (it supersedes our earlier loop band-aids), keep
only orthogonal unique fixes:
- codex bundled-JS launcher fix (codex-warmup.ts)
- slot-aligned Claude+Codex usage primer (usage-primer.ts) re-wired into index.ts
- MemoryHigh=3G cgroup bound, discord perms diagnostic, prompt docs
- progress null-race + silent-failure publish guards (message-turn-controller.ts)

Dropped (superseded by upstream or unwired): reviewer STEP_DONE/TASK_DONE loop
band-aids, router markdown-escape override, register tribunal-default+git-init,
restart-context rewindToSeq (unwired).

Verified: typecheck clean, build clean, vitest shows zero new regressions vs the
origin/main baseline (only pre-existing env-config failures remain).

.claude/skills/setup/SKILL.md

@@ -56,7 +56,7 @@ Codex 관련 선택 설정은 **별도 서비스 파일이 아니라 같은 `.en
 
 ```bash
 # 같은 .env 또는 서비스 Environment=에 추가 가능
-CODEX_MODEL=gpt-5.4
+CODEX_MODEL=gpt-5.5
 CODEX_EFFORT=xhigh
 OPENAI_API_KEY=...
 ```