refactor: extract model selection logic from delegate-task into focused modules

- Create available-models.ts for model availability checking
- Create model-selection.ts for category-to-model resolution logic
- Update category-resolver, subagent-resolver, and sync modules to import
  from new focused modules instead of monolithic sources

src/tools/delegate-task/sync-task.ts

@@ -4,7 +4,7 @@ import type { ExecutorContext, ParentContext } from "./executor-types"
 import { getTaskToastManager } from "../../features/task-toast-manager"
 import { storeToolMetadata } from "../../features/tool-metadata-store"
 import { subagentSessions } from "../../features/claude-code-session-state"
-import { log } from "../../shared"
+import { log } from "../../shared/logger"
 import { formatDuration } from "./time-formatter"
 import { formatDetailedError } from "./error-formatting"
 import { createSyncSession } from "./sync-session-creator"