perf: round 9 — decorator PUT reactivation, session/search/dedup alloc purges, PROPFIND join!, folder-level cascade

Benchmark-gated round (benches/ROUND9.md): every change carries a
BEFORE/AFTER bench with equivalence/safety gates; verdicts below are from
the committed harnesses on 4 cores / local PG 16.

Backend:
- Blob decorators (Retry/Cached) now forward put_blob_from_bytes_unsynced
  + sync_blobs — the trait default had silently reinstated HEAD-before-PUT
  per chunk on decorated remote stacks, undoing ROUND3 §8. Full production
  stack: 500 probes -> 0, 1.9x wall at 10 ms RTT (bench_s3_put §3).
- NC PROPFIND per-page enrichment triple (favorites / oc:fileid / dead
  props) overlapped with tokio::join!: 2.07x local, 2.86x at 5 ms RTT
  (bench_nc_enrich_join, injected-latency decide-by-bench).
- Search enrichment consumes its DTOs and carries the interned Arc<str>
  display fields end-to-end (SearchFileResultDto type change, OpenAPI
  shape preserved): enrich_file 2.0x, 11.6 -> 2.2 allocs/row; the NC
  REPORT conversion stops re-running all three classifiers per row
  (bench_search_enrich).
- NC session Arc end-to-end: SharedNcSession extractor (8 -> 0 allocs),
  Arc<FolderDto> chroot cache (4 -> 0/hit), single shared Arc<CurrentUser>
  + lazy span render (11 -> 6/build) (bench_nc_session).
- Storage micro-pack: atomic create_new chunk writes (2.1x fresh),
  stream_chunks over the manifest Arc (4097 -> 0 allocs/read incl. the
  Range path), manifest single-flight (herd 64 -> 1 loads), hex_lower for
  chunk Content-MD5 (18 -> 1 allocs) (bench_storage_micro).
- OCS capabilities memoized into OnceLock<[Bytes;2]>: 237x, 102 -> 0
  allocs/poll, byte-identical (bench_capabilities_static).
- Drive::is_empty COUNT(*) sum -> EXISTS: 34.4x on a 100k-file drive
  (bench_drive_is_empty).
- favorites/recents row-map ROUND7 port: path/name/blob_hash moved,
  -2.75 allocs/row (bench_resource_row_map §2).
- Folder rows decode binary UUIDs (ROUND6 §10 port): 1.03-1.07x page
  fetch, honest verdict incl. one noise-band wash documented
  (bench_folder_uuid_decode).
- Authz: file cascade decision decomposed into memoized folder-level
  decision + direct-grant lookup (ROUND8 deferred item). Cold shared-album
  first view 592 -> 418 µs/thumb; warm path unchanged; safety gates incl.
  new direct-grant sibling isolation, revoke-flush re-verified, full
  integration authz suite green (bench_thumbnail_cascade_cache).

Frontend (vitest gates committed beside the code):
- resolveLabel/resolveRecipient O(directory) scan -> id-keyed Map: 13.9x
  (recipients.bench.test.ts).
- ResourceList selection-prune effect skips when nothing is selected
  (100 -> 0 Set builds per drain) and the photos timeline reads a
  listener-fed mobile flag instead of matchMedia per recompute
  (listDerives.bench.test.ts).

Verification: cargo fmt + clippy --all-features --all-targets -D warnings
clean; 524 unit + 554 integration (--cfg integration_tests) tests pass;
frontend npm run check clean with 293 vitest tests green.

Deferred with rationale in ROUND9.md: CalDAV authz-before-fetch reorder
(maintainer sign-off), per-page batched parent resolution, JWT-claims
Arc<str>, batch_operations signature widening.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XDc9VtXvskJ6dnMRraSndn

frontend/src/lib/api/endpoints/recipients.ts

@@ -134,10 +134,26 @@ export async function ensureResolvers(): Promise<void> {
 	await Promise.all([systemContacts(), loadGroups()]);
 }
 
+// O(1) id→contact index over `contactCache`, built once per cache identity.
+// `resolveLabel`/`resolveRecipient` run per rendered grant row on /shared —
+// the previous `contactCache.find(...)` linear scan made each render frame
+// O(rows × directory size).
+let contactById: Map<string, Contact> | null = null;
+let contactByIdSource: Contact[] | null = null;
+
+function contactIndex(): Map<string, Contact> | null {
+	if (!contactCache) return null;
+	if (!contactById || contactByIdSource !== contactCache) {
+		contactById = new Map(contactCache.map((c) => [c.id, c]));
+		contactByIdSource = contactCache;
+	}
+	return contactById;
+}
+
 /** Resolve a subject id to a display label using the preloaded caches. */
 export function resolveLabel(type: 'user' | 'group', id: string): string {
 	if (type === 'group') return groupCache?.get(id) ?? id;
-	const c = contactCache?.find((x) => x.id === id);
+	const c = contactIndex()?.get(id);
 	return c ? contactLabel(c).label : id;
 }
 
@@ -146,7 +162,7 @@ export function resolveRecipient(type: 'user' | 'group', id: string): Recipient
 	if (type === 'group') {
 		return { type: 'group', id, label: groupCache?.get(id) ?? id };
 	}
-	const c = contactCache?.find((x) => x.id === id);
+	const c = contactIndex()?.get(id);
 	if (!c) return { type: 'user', id, label: id };
 	const { label, email } = contactLabel(c);
 	return { type: 'user', id, label, sublabel: email };