test: keep review assertions tied to real failure paths

CodeRabbit flagged three non-blocking but valid review gaps: platform-specific mailbox errno checks, brittle UDS connection-failure message assertions, and missing AgentSummary reschedule proof after fork errors. This keeps the fixes narrow by tightening the affected assertions and adding a structured UDS connection error for tests to assert behavior instead of prose.

Constraint: PR #374 is a review follow-up and must not hide warnings, skip tests, or merge the PR.

Rejected: Matching the UDS failure message literal | preserves the brittle coupling CodeRabbit flagged.

Rejected: Asserting only that mailbox writes throw | would allow unrelated pre-path failures to pass.

Confidence: high

Scope-risk: narrow

Directive: Keep UDS connection-failure tests on structured error data, not display wording.

Tested: bun test src/services/AgentSummary/__tests__/agentSummary.test.ts src/utils/__tests__/teammateMailbox.test.ts src/utils/__tests__/udsMessaging.test.ts

Tested: bunx tsc --noEmit --pretty false

Tested: bun run lint

Tested: bun run test:all

Tested: bun test --coverage --coverage-reporter lcov --coverage-dir coverage

Tested: bun run build

Tested: bun run build:vite

Not-tested: GitHub-hosted CodeRabbit refresh until pushed.

src/utils/__tests__/udsMessaging.test.ts

@@ -227,11 +227,20 @@ describe('UDS inbox retention', () => {
       JSON.stringify({ socketPath: path, authToken: 'test-token' }),
       'utf-8',
     )
-    const { sendToUdsSocket } = await import('../udsClient.js')
-
-    await expect(sendToUdsSocket(path, 'hello')).rejects.toThrow(
-      'Failed to connect to peer',
+    const { sendToUdsSocket, UdsPeerConnectionError } = await import(
+      '../udsClient.js'
     )
+
+    const error = await sendToUdsSocket(path, 'hello').then(
+      () => undefined,
+      err => err,
+    )
+    expect(error).toBeInstanceOf(UdsPeerConnectionError)
+    if (!(error instanceof UdsPeerConnectionError)) {
+      throw new Error('Expected UDS peer connection error')
+    }
+    expect(error.socketPath).toBe(path)
+    expect(error.message).not.toContain('test-token')
   })
 
   test('sendUdsMessage fails closed before connecting without an auth token', async () => {