docs: perf roadmap remainder — outcomes + follow-up register

CLAUDE.md

@@ -748,15 +748,18 @@ Two things to know before relying on any of this:
     *current* generation rather than the one the session activated under, and re-checks the
     authenticating key — so revoking a key or a grant stops an open session immediately instead of at
     the client's next reconnect. On a driver-only node the artifact is the only revocation channel.
-  - `UserAuthorizationState` is built **per call, not per session**, and its LDAP-shaped
+  - `UserAuthorizationState` is built **per decision walk, not per session** — and since the hot-path
+    change it is allocated only on a cache **miss**, so a cache hit never constructs one. Its LDAP-shaped
     freshness/staleness predicates are switched off EXPLICITLY (`AuthCacheMaxStaleness = MaxValue`).
     ⚠️ Relying on "the stamp is always fresh" was not safe: `MembershipResolvedUtc` comes from
     `DataPlaneAuthorizer`'s `TimeProvider` while `IsStale` is evaluated against
     `TriePermissionEvaluator`'s, so **any divergence between the two clocks denies every request** with a
     verdict indistinguishable from "no grant matched". Found by a test clock two hours ahead.
   - **Stage 6's hot seams (read/browse/subscribe) go through a per-`(session, node, operation, realm)`
-    decision cache**, flushed when the generation advances. ⚠️ It caches the **grant walk only** — key
-    revocation and expiry are re-checked every call, because expiry moves with the clock rather than
+    decision cache**, cleared wholesale when the generation advances. It is **sharded per session**, so a
+    single client crawling a large tree past the per-session ceiling evicts only its own shard and not
+    every other session's decisions. ⚠️ It caches the **grant walk only** — key revocation and expiry are
+    re-checked **before** the cache lookup on every call, because expiry moves with the clock rather than
     with a deployment.
   - **Browse needs ancestor visibility, and it must NOT be a synthesized grant on the ancestors.** A
     grant deep in the tree is reached by browsing the nodes above it, and the trie inherits downward