docs(adr): ratify ADR-0009 amendment — shared spend accounting

Maintainer accepted 2026-07-05. Step 6 builds the gate against a
check-and-reserve ledger trait: in-memory at N=1, Valkey at N>1.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012QndwfhjyTiZcUYp87dwW8
Signed-off-by: Aaron D. Lee <himself@adlee.work>

docs/adr/0009-spend-gate-honest-rescope.md

@@ -84,7 +84,7 @@ security-constitutive), but its guarantees are restated precisely:
 
 ## Amendment 2026-07-04 — enforcement locality ≠ accounting locality
 
-- **Status:** Proposed (pending maintainer ratification)
+- **Status:** Accepted (maintainer-ratified 2026-07-05)
 - **Origin:** [2026-07-04 scalability & infra-fit review](../reviews/2026-07-04-scalability-infra-review.md),
   finding M5.