perf: round 10 — auth alloc purge, parent-herd batching, query-shape pack, NC 304s

Benchmark-gated (benches/ROUND10.md; every change carries a BEFORE/AFTER
harness with equivalence/safety gates — two designs were rejected or
rewritten by their own benches before adoption):

- Auth hot path: TokenClaims/CurrentUser display fields to Arc<str>, role
  to inline SmolStr end-to-end (Bearer, cookie, Basic-auth cache) — 4→1
  allocs per authenticated request, 3→0 per warm DAV request; JWT
  Encoding/Decoding/Validation built once.
- Cold shared-album herd: leader-inline parent batching in PgAclEngine
  (+ cascade try_get_with single-flight) — 100→2 parent queries per
  100-thumb cold herd, herd wall 1.9x, sequential + warm paths unchanged,
  all ROUND8/9 safety gates plus new herd-equivalence gates.
- Query-shape pack: share download double-fetch 2→1 (2.18x), contact-group
  COUNT(*) 14.9x, save_faces UNNEST 3.9x, playlist reorder UNNEST 63.7x
  (now atomic), search files∥folders join! 1.45x, move drive-lookup join!
  2.14x, trash partial (drive_id, trashed_at) indexes, CalDAV event-gate
  narrow read, favorites/recents binary-decode port, dead count_files
  removed.
- NC surface: preview + avatar honour If-None-Match (e2e: 5 KB and 197 KB
  → 0 bytes per revalidation), avatar WebP→PNG transcode memoised,
  PROPFIND/trashbin integer+date emits on stack formatters, folder-header
  enrichment join!, chunk-PUT retry stat folded into create_new open.
- common::fmt integer rendering rewritten on the std 2-digit LUT after the
  round's own bench caught the div-loop losing to to_string (16.1 ns vs
  22.5; speeds every prior-round call site).
- Micro-pack: WebDAV scope probe borrow-only, ShareService base_url
  snapshot, cookie_secure OnceLock, Arc'd AES-GCM cipher, stack request-id,
  tantivy analyzer clone dropped.
- SPA: search stale-guard + AbortController (10→1 completed round-trips,
  stale-clobber gone), getFolder in-flight dedup, gridColumns matchMedia
  hoist (10k→0 style reads).

Backend: cargo fmt + clippy -D warnings clean, 524 tests green.
Frontend: npm run check clean, 301 vitest green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018DdM7V7M3QPW7HEHg3gLov

Cargo.toml

@@ -37,7 +37,7 @@ chrono = { version = "0.4.45", features = ["serde"] }
 # component. If a spec conformance gap is found, we contribute upstream.
 ical = "0.11"
 http-body = "1.0.1"
-serde = { version = "1.0.228", features = ["derive"] }
+serde = { version = "1.0.228", features = ["derive", "rc"] }
 serde_json = "1.0.150"
 futures = "0.3.32"
 async-stream = "0.3.6"
@@ -350,6 +350,25 @@ name = "bench_micro_allocs"
 path = "examples/bench_micro_allocs.rs"
 required-features = ["bench"]
 
+# Round-10 battery ────────────────────────────────────────────────────────────
+
+# Round-10 CPU/alloc micro-pack — auth identity build, basic-auth hit,
+# PROPFIND/trashbin int+date emits, webdav scope probe, base_url snapshot,
+# JWT verify-miss keys, cipher Arc, request-id. No Postgres.
+[[example]]
+name = "bench_round10_micro"
+path = "examples/bench_round10_micro.rs"
+required-features = ["bench"]
+
+# Round-10 query-shape pack — share download double-fetch, calendar-id narrow
+# read, contact-group COUNT, trash partial indexes, favorites/recents binary
+# UUID decode, save_faces UNNEST, playlist reorder UNNEST, search 3-query
+# join!, move drive-lookup join! (needs the dev Postgres up).
+[[example]]
+name = "bench_round10_queries"
+path = "examples/bench_round10_queries.rs"
+required-features = ["bench"]
+
 # Round-9 battery ─────────────────────────────────────────────────────────────
 
 # Search enrichment — borrow+clone+reclassify vs consume+carry (file/folder