feat(FN-829): persist triage model selection into agent log

- Log the selected model provider and ID during triage so the agent log records which model was used
- Add agent-log entry capturing triage model choice for observability
- Add comprehensive tests for triage model logging behavior
- Update AgentsView component and dashboard docs for consistency
- Remove obsolete AgentsView test

packages/engine/src/restart.integration.test.ts

@@ -81,6 +81,7 @@ function createMockStore(overrides: Record<string, any> = {}) {
       return makeTask(id, col);
     }),
     logEntry: vi.fn().mockResolvedValue(undefined),
+    appendAgentLog: vi.fn().mockResolvedValue(undefined),
     parseStepsFromPrompt: vi.fn().mockResolvedValue([]),
     parseFileScopeFromPrompt: vi.fn().mockResolvedValue([]),
     getSettings: vi.fn().mockResolvedValue({ ...DEFAULT_SETTINGS }),