Make `newInternalTestServer` use option functions for logger, clock, and
worker startup, and make it passive by default so internal chatd tests
only opt into background execution when they need a real worker.
Use the passive server path in `TestAwaitSubagentCompletion` for the
state-driven subtests, keep `ContextCanceled` explicitly active for real
provider cancellation coverage, and keep the fail-fast default AI
provider base URL so accidental provider calls still fail immediately.
Closes CODAGT-586
Closes https://github.com/coder/internal/issues/1549
Ethan
35af54d6aa