docs(worktrees): explain create fetch maintenance scope

src/main/ipc/worktree-remote.ts

@@ -478,6 +478,7 @@ async function refreshRemoteTrackingBaseForWorktreeCreate(
     getSshWorktreeCreateBaseFetchKey(repo, base),
     getSshWorktreeCreateRemoteQueueKey(repo, base.remote),
     () =>
+      // Why: the exact-base refresh gates create; unrelated repo housekeeping must not extend it.
       provider.fetchRemoteTrackingRef(repo.path, base.remote, base.branch, base.ref, {
         skipAutoMaintenance: true
       })

src/main/runtime/orca-runtime.ts

@@ -14621,6 +14621,7 @@ export class OrcaRuntimeService {
       if (this.getFreshFetchCompletedAt(key) !== null) {
         return { ok: true }
       }
+      // Why: this exact refresh gates worktree create; ordinary fetches still own maintenance.
       return gitExecFileAsync(
         [
           ...GIT_FETCH_SKIP_AUTO_MAINTENANCE_CONFIG_ARGS,