fix(server): keep the authoritative subagent model when snapshots race task_started - #7583

💭 I'm looking at the diff in ClaudeAdapter.ts, an Effect service that now adds a Map for pending task models plus a helper function. I want to check this against conventions around imports, service definition, dependency acquisition, and error handling, so I'm pulling up the file to verify the surrounding context. Imports look fine. Now I want to check the modified sections of the existing service for convention issues, so I'll look around lines 2900-2940 and 3230-3260. This is a behavioral change within an existing service, so no new Effect service, errors, imports, or Layer patterns are needed—just a focused test covering the behavior change. I should double-check that the test file's imports for Effect, Stream, Fiber, and Random are already consolidated properly. The ClaudeAdapterShape in the adapter file is pre-existing legacy code untouched by this PR, so it's out of scope for review. I don't see any violations, so I'll format the response as JSON with a success state and "All clear" as the summary, since the schema requires structured output rather than a plain string.