[codex] Add TUI registry foundation and harden handoffs

[windoliver]

Summary

• Keep the existing TUI registry/plugin foundation for DX: adopt OpenCode TUI patterns and Goose agent organization concepts for multi-agent collaboration #225 on this branch.
• Harden review-loop handoffs by tracking ACP runtime status through running/idle/crashed transitions and surfacing agent crashes to the orchestrator.
• Register local Grove sessions before MCP-backed agents start, resolve grove mcp serve through the active Bun executable, and make required role spawning all-or-nothing.
• Wait for ACP turns to settle before stopping achieved sessions so Codex -> Claude handoffs persist their work/review/done contributions.

Part of #225. Full remaining #225 scope is split into follow-up issues #440 through #447, with existing related trackers #189, #212, #193, #194, #275, and #276.

Validation

• PATH="$HOME/.bun/bin:$PATH" bun run typecheck
• PATH="$HOME/.bun/bin:$PATH" bun run check (passes with existing warnings)
• PATH="$HOME/.bun/bin:$PATH" bun run build
• git diff --check
• PATH="$HOME/.bun/bin:$PATH" bun test src/core/resolve-mcp-serve-path.test.ts src/core/acp-runtime.spawn.test.ts src/core/session-orchestrator.test.ts --timeout 60000 -> 62 pass / 0 fail; Bun exits 1 because repo coverage thresholds are global and this is a partial test run.
• Live Codex -> Claude SessionOrchestrator validation completed with 3 linked contributions: Codex work, Claude review, and Claude [DONE] approval.
• Tmux TUI e2e validation could not run literally because tmux is not installed in this environment; related e2e files were not included in this commit.

Notes

• The branch already had PR [codex] Add TUI registry foundation and harden handoffs #435 open, so this updates that PR instead of creating a duplicate PR from the same head branch.