feat: add persistent governed Codex coworker

[FsDevNinja]

Summary

• add a host-side AG-UI adapter that uses the locally authenticated Codex app-server and ChatGPT subscription
• persist the OpenBot-thread to Codex-thread join atomically, resume the exact Codex thread after adapter/app-server restarts, and refuse corrupt recovery state instead of silently starting over
• expose only OpenBot deployment-owned tools as Codex dynamic tools, then execute every call through the existing signed /api/agent-tools/call grant, policy, and audit boundary
• disable Codex MCP, app, plugin, web, hook, memory, and multi-agent capabilities; run turns read-only without network and interrupt native action attempts
• reject stale, malformed, unexpected, and duplicate callbacks; cancel the Codex turn and gateway request when OpenBot ends the run
• install the host adapter from the root workspace and document/configure the local Codex mode

Verification

• bun run lint
• bun run format:check
• bun run typecheck
• bun run build
• bash -n scripts/start.sh
• bun test --coverage agent-codex/tests tests/workspace.test.ts — Codex source: 98.91% lines overall, 97.68% in the app-server client
• real installed Codex app-server: dynamic callback completed through the adapter
• real installed Codex app-server: a second app-server process resumed the same thread ID and recalled the prior turn

The full local suite reached 2,155 pass / 23 skip. Five existing tests outside this diff failed locally: two agent-bot startup tests cannot resolve that non-workspace package's local @ag-ui/encoder, and three existing handoff integration cases failed against the shared test database. This PR changes no server or handoff source/test files.

Notes

Codex dynamic tools are currently an experimental app-server capability. The adapter enables that protocol explicitly and fails closed when it cannot establish the required ChatGPT account, recovery state, or OpenBot callback credentials.