feat(ui): PeerFiles renders from the shared peer-browse cache (B4)

- PeerFiles.vue reads the SAME `cloud.peer-browse:<onion>` entry Cloud.vue's
  per-peer fan-in fills, so Cloud → peer files paints instantly from cache
  and revalidates behind it; catalog/error/loading/transport are now
  computed views over the store entry.
- preview-peer fan-out is capped at 3 concurrent with a queue (was one 30s
  RPC per media item, all at once, unbounded) and aborts on unmount.
- browse + preview RPCs drop to maxRetries:1 — retry×3 turned one slow
  peer into a 90s spinner.
- fix useCachedResource's interface types: `ReturnType<typeof computed<T>>`
  resolves to the writable overload (WritableComputedRef), which broke
  vue-tsc against the plain computed() returns; use ComputedRef<T>.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

neode-ui/src/composables/useCachedResource.ts

@@ -22,7 +22,7 @@
 // - Abort-on-unmount: the fetcher receives an AbortSignal that fires when
 //   the last subscribed component unmounts.
 
-import { computed, getCurrentScope, onScopeDispose } from 'vue'
+import { computed, getCurrentScope, onScopeDispose, type ComputedRef } from 'vue'
 import { useResourcesStore, type ResourceEntry, type ResourceLoadState } from '@/stores/resources'
 
 export interface CachedResourceOptions<T> {
@@ -44,12 +44,12 @@ export interface CachedResourceOptions<T> {
 export interface CachedResource<T> {
   entry: ResourceEntry<T>
   /** Convenience computed views over the entry. */
-  data: ReturnType<typeof computed<T | null>>
-  loadState: ReturnType<typeof computed<ResourceLoadState>>
-  error: ReturnType<typeof computed<string | null>>
+  data: ComputedRef<T | null>
+  loadState: ComputedRef<ResourceLoadState>
+  error: ComputedRef<string | null>
   /** True when data exists but is older than the TTL (drive an age badge). */
-  isStale: ReturnType<typeof computed<boolean>>
-  ageMs: ReturnType<typeof computed<number | null>>
+  isStale: ComputedRef<boolean>
+  ageMs: ComputedRef<number | null>
   /** Force a refresh now (deduped with any in-flight one). */
   refresh: () => Promise<void>
   /** Mark stale + debounce-refresh all mounted users of this key. */