feat: add in-flight guard and attach hook scoping

[chriswritescode-dev]

Summary

• Add in-flight guard to prevent concurrent loop execution, rejecting duplicate prompts when a prior agent session is still running.
• Scope the attach hook to support loop inline plan and execution attach cleanup, improving cross-project session resolution and preventing stale state propagation.

Changes

New files:

• src/loop/in-flight-guard.ts — Concurrent prompt detection via a shared Map tracking per-loop in-flight sessions; throws ConcurrentPromptError on conflicts.
• test/loop/in-flight-guard.test.ts — Unit tests for the guard logic (mark/clear/assert lifecycle).
• test/loop/runtime.test.ts, test/services/execution-in-flight-guard.test.ts, test/services/execution-attach-cleanup.test.ts — Integration tests exercising the full runtime path.

Modified files:

• src/hooks/forge-session-attach.ts — Refactored attach-scoping to align with loop inline plan state.
• src/loop/runtime.ts — Integrated in-flight guard checks before prompt dispatch.
• src/services/execution.ts — Enhanced execution pipeline to invoke the guard.
• src/utils/tui-client.ts — Updated TUI client hooks to reflect scoped cleanup signals.
• Various test files — Updated or added tests covering audit permissions, loop status tool, and warp flow edge cases.

All tests pass locally via vitest.

Checklist

• Branch is up-to-date with origin/main
• Tests pass
• Reviewers assigned (pending)