test(coderd/x/chatd): pin the debug runs that turns, titles and status labels record - #30933

Adds tests that pin what four call sites record when they create and finalize a debug run: chat turns, manual titles, automatic titles and turn status labels. #30934 moves all four onto one helper. Automatic titles and status labels had no debug-run test, and the chat turn and manual title tests checked only some fields.

• TestRunnerDebugTurnEnsureCreatesOnce now checks every insert parameter, the full RunContext the model call sees, and that the insert runs on a context that ignores the caller's cancellation but has a deadline.
• New TestRunnerDebugTurnEnsureCreateFailureDisablesTurn: a failed insert disables debug for the turn, and the turn does not retry it.
• TestProposeChatTitle_DebugRun also checks that the run has no trigger message, its model config and model, the seed label in its summary, and that it recorded steps.
• New TestQuickgenDebugRun covers automatic titles and status labels when the model succeeds, when it fails, and when the insert fails. It checks the insert, the run context and the finalize call. Titles record the configured provider and model; status labels record the resolved ones.
• New TestPrepareManualTitleDebugRunCreateFailure: when the manual title insert fails, the title call gets no run and finishing does nothing.

Why it is safe: the PR changes only tests, and they pass on main's production code. To show they can fail, I ran 34 mutants of the four call sites, and 31 fail the new tests. Two survivors change nothing these tests can observe: the seed summary on the manual title insert (finalize rewrites the summary) and the 10 second finalize timeout for titles and labels. This layer does not pin the third: removing context.WithoutCancel from the title and label insert in quickgen.go. #30934 moves that detach into the shared BeginRun, which the chat turn test pins.

Validation: go test -race -count=1 -p 4 -parallel 4 ./coderd/x/chatd/ -run '^(TestRunnerDebugTurn.*|TestProposeChatTitle_DebugRun|TestQuickgenDebugRun|TestPrepareManualTitleDebugRunCreateFailure)$' passes on this branch and with main's production code, and the pre-commit hook passed.

Stack

This stack simplifies the chatdebug heartbeat, debug-run and stream wrapper code. Each refactor sits on a test-only layer that pins the behavior it keeps.

1. test(coderd/x/chatd/chatdebug): cover both debug heartbeat launchers #30931 Cover both debug heartbeat launchers
2. refactor(coderd/x/chatd): set the chatdebug stale threshold at construction #30932 Set the chatdebug stale threshold at construction
3. test(coderd/x/chatd): pin the debug runs that turns, titles and status labels record #30933 Pin the debug runs that turns, titles and status labels record
4. refactor(coderd/x/chatd): create and finalize debug runs through one helper #30934 Create and finalize debug runs through one helper
5. test(coderd/x/chatd/chatdebug): table the stream wrapper tests and cover their status rules #30980 Table the stream wrapper tests and cover their status rules
6. refactor(coderd/x/chatd/chatdebug): share one finalize-once lifecycle between the stream wrappers #30981 Share one finalize-once lifecycle between the stream wrappers

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