feat: implement issue spawn rejection for closed or cancelled states

[nikhilachale]

Summary

This PR prevents AO from spawning new worker sessions for tracker issues that are already closed or cancelled.

Previously, spawn requests could continue even when the linked tracker issue was no longer actionable. The session manager now checks
the resolved issue state before creating a workspace or runtime, records a rejection activity event, and throws a typed
IssueNotSpawnableError.

Changes

• Added IssueNotSpawnableError for closed/cancelled issue spawn attempts
• Added isSpawnableIssueState() helper for spawn-eligible issue states
• Updated SessionManager.spawn() to reject closed or cancelled tracker issues before workspace/runtime creation
• Updated /api/spawn to return 409 Conflict for non-spawnable issues instead of 500
• Added API/activity metadata for rejected spawn attempts
• Added session manager tests for:
  • rejecting closed issues
  • rejecting cancelled issues
  • allowing in_progress issues

Testing

• Added coverage in packages/core/src/__tests__/session-manager/spawn.test.ts

[greptile-apps]

Greptile Summary

This PR adds a spawn guard that rejects new worker sessions for tracker issues already in a closed or cancelled state, returning a typed IssueNotSpawnableError and HTTP 409 instead of letting the spawn proceed and fail later.

• types.ts introduces isSpawnableIssueState() and IssueNotSpawnableError; session-manager.ts calls the guard immediately after issue resolution, before any workspace or runtime resources are created; route.ts maps the error to 409 and enriches the API observation with rejection metadata.
• Tests cover the two rejection states (closed, cancelled) and one pass-through state (in_progress), though the "open" state is not explicitly exercised.

Confidence Score: 5/5

Safe to merge — the guard fires before any resources are created, the error is correctly typed and caught at the API boundary, and existing spawn paths for valid issue states are unaffected.

The change is narrowly scoped: it adds a single pre-flight check that short-circuits before touching the workspace or runtime, wires a new typed error to a 409 response, and includes tests for the rejection cases. No existing behaviour is altered for spawnable issues.

No files require special attention; the test file is missing coverage for the "open" spawnable state but this does not affect correctness of the guard itself.

Important Files Changed

Filename	Overview
packages/core/src/types.ts	Adds isSpawnableIssueState() guard and IssueNotSpawnableError class; both are well-typed and consistent with the existing Issue["state"] union.
packages/core/src/session-manager.ts	Adds pre-resource-creation spawn guard that fetches the issue state and throws IssueNotSpawnableError for non-spawnable states; logic is correct and well-placed after the existing issue-fetch try/catch.
packages/web/src/app/api/spawn/route.ts	Maps IssueNotSpawnableError to HTTP 409 and enriches recordApiObservation with issue state metadata; straightforward and correct.
packages/core/src/tests/session-manager/spawn.test.ts	Adds three new spawn-guard tests covering closed, cancelled, and in_progress; missing a test for the "open" spawnable state.

Sequence Diagram

sequenceDiagram
    participant Client
    participant SpawnRoute as /api/spawn
    participant SessionManager
    participant Tracker

    Client->>SpawnRoute: "POST /api/spawn { projectId, issueId }"
    SpawnRoute->>SessionManager: "spawn({ projectId, issueId })"
    SessionManager->>Tracker: getIssue(issueId, project)
    Tracker-->>SessionManager: "Issue { state }"

    alt state is closed or cancelled
        SessionManager->>SessionManager: recordActivityEvent(session.spawn_rejected)
        SessionManager-->>SpawnRoute: throw IssueNotSpawnableError
        SpawnRoute->>SpawnRoute: recordApiObservation(failure, 409)
        SpawnRoute-->>Client: 409 Conflict
    else state is open or in_progress
        SessionManager->>SessionManager: create workspace + runtime
        SessionManager-->>SpawnRoute: Session
        SpawnRoute-->>Client: 201 Created
    end

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Prompt To Fix All With AI

Fix the following 2 code review issues. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 2
packages/core/src/__tests__/session-manager/spawn.test.ts:1151-1163
The test suite covers `closed`, `cancelled`, and `in_progress` but skips the `"open"` state, which is the other explicitly spawnable value in `isSpawnableIssueState`. Without it, a regression that accidentally blocks `"open"` issues would go undetected by these tests.

```suggestion
  it("allows spawn when tracker issue is in_progress", async () => {
    const mockTracker = baseMockTracker({ id: "INT-50", state: "in_progress" });
    const sm = createSessionManager({
      config,
      registry: registryWithTracker(mockTracker),
    });

    const session = await sm.spawn({ projectId: "my-app", issueId: "INT-50" });

    expect(session.issueId).toBe("INT-50");
    expect(mockWorkspace.create).toHaveBeenCalled();
    expect(mockRuntime.create).toHaveBeenCalled();
  });

  it("allows spawn when tracker issue is open", async () => {
    const mockTracker = baseMockTracker({ id: "INT-51", state: "open" });
    const sm = createSessionManager({
      config,
      registry: registryWithTracker(mockTracker),
    });

    const session = await sm.spawn({ projectId: "my-app", issueId: "INT-51" });

    expect(session.issueId).toBe("INT-51");
    expect(mockWorkspace.create).toHaveBeenCalled();
    expect(mockRuntime.create).toHaveBeenCalled();
  });
```

### Issue 2 of 2
packages/core/src/types.ts:2008-2010
The error message hardcodes `"closed/cancelled"`, so if a new non-spawnable state is ever added to `Issue["state"]` and `isSpawnableIssueState` is updated, the static text here will silently misrepresent the actual rejection reason. Interpolating `state` directly keeps the message accurate regardless of how many non-spawnable states exist.

```suggestion
    super(
      `Issue ${issueId} is ${state}. Cannot spawn a session for a ${state} issue.`,
    );
```

_{Reviews (2): Last reviewed commit: "refactor: enhance issue state handling i..." | Re-trigger Greptile}