test(coderd/x/chatd): reuse recordingPubsub in the task test fixture - #30923

tasks_test.go kept its own copy of the recording pubsub, taskRecordingPubsub (59 lines), next to recordingPubsub in helpers_test.go. This PR adds the three things the copy had (clear, a published snapshot and an onPublish hook) to recordingPubsub, points the task fixture at it, and deletes the copy. The task fixture now reaches the raw pubsub through the embedded field, so its rawPS field goes too.

Why it is safe

• The added methods behave like the copy's: onPublish runs outside the lock and before the inner Publish, clear drops the recorded events, and published returns a copy taken under the lock. It replaces the copy's events(), which would collide with the existing events field.
• recordingPubsub embeds the full dbpubsub.Pubsub, so subscriptions reach the same inner pubsub the copy forwarded SubscribeWithErr to. Servers built by the task helpers still get the raw pubsub.
• watchEvents is the existing recordingPubsub method. It filters the same way the copy did, reading under the lock instead of from a snapshot.
• After the change, rg 'taskRecordingPubsub|taskPublishedEvent|rawPS' coderd/ finds nothing.

Review focus

The turn-trace tests set f.pubsub.onPublish while holding f.pubsub.mu. Both names are unchanged, and Publish still reads the hook under that lock.

Validation

I built the package test binary with go test -c ./coderd/x/chatd/ (and with -race). Ten files use either fixture: tasks_test.go, hooks_internal_test.go, turn_trace_internal_test.go and the seven workerTestFixture files. I ran the 142 top-level tests in the ten files with -test.count=1 -test.parallel 4.

The pre-commit hook passed.

Stack

The stack folds the task test fixture into the shared worker test fixture.

1. test(coderd/x/chatd): reuse recordingPubsub in the task test fixture #30923 reuse recordingPubsub in the task test fixture (this PR)
2. test(coderd/x/chatd): fold taskTestFixture into workerTestFixture #30924 fold taskTestFixture into workerTestFixture

Xum, an AI agent, opened this PR for @ibetitsmike and wrote this description.