FABRIC-3.md: close stale ACL-RWT re-measurement item -- already done in §T

Corrects bookkeeping, not measurement. FABRIC-2.md Sections M-T
(2026-08-19/21) already re-ran this and found the original "ACL-RWT"
name was itself wrong -- the Rolling-Window-of-Truth mechanism it
named was dead code removed 2026-07-08, never reachable. What the
campaign actually measured was the live ACL-TTL mechanism. Final
accepted result: +0.0603% ACL-TTL enforcement overhead,
architecture-independent, CV=0.000% (FABRIC-2.md SS T,
project_acl_ttl_overhead_final.md). The checkbox was simply never
marked done when that work concluded -- no new campaign run.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CXjAPTEKrgY2Mrk25KoLDn

FABRIC-3.md

@@ -56,12 +56,17 @@ decisions get added here, not to `FABRIC-2.md`. Follow the same discipline `FABR
 
 ### From FABRIC-2.md §E — Documentation debt
 
-- [ ] **ACL-RWT DoE overhead re-measurement.** The measured overhead numbers in
-  `.claude/CLAUDE.md` ("+0.0054%–+0.0088%") were all captured at `-O0`, before item 4.5
-  enabled real compiler optimization. Nobody has re-measured, or even confirmed the old and
-  new numbers are comparable at all. Flagged in passing during item 4.5f, never formally
-  scoped. **Ruled 2026-08-19 (`FABRIC-2.md` §F.3): wait for Artemis to land before
-  re-running** — Artemis has since landed; this is now unblocked but still not started.
+- [x] **Already done — stale carry-forward, closed 2026-08-26.** This item was never marked
+  complete when the actual work concluded. `FABRIC-2.md` Sections M through T (2026-08-19 to
+  2026-08-21) already re-ran this measurement — and in the process found the original
+  "ACL-RWT" name itself was wrong: the Rolling-Window-of-Truth mechanism it was named after
+  was dead code, removed 2026-07-08 (`ACL-RECHECK-RW` was never reachable — `acl_recheck()`
+  only ever looks up the 11-char `ACL-RECHECK`, never the 14-char `-RW` variant). What the
+  original campaign actually measured was the live `ACL-TTL` mechanism under a misleading
+  name. **Final, accepted result (`FABRIC-2.md` §T): +0.0603% ACL-TTL enforcement overhead,
+  architecture-independent (identical across amd64/aarch64/riscv64), fully deterministic
+  (CV=0.000%)** — see also memory `project_acl_ttl_overhead_final.md`. No new campaign run
+  here; this entry corrects the bookkeeping, not the measurement.
 
 ### From FABRIC-2.md §J — Maintainability sweep (2026-08-18)