docs: fix CHANGELOG.md SPEC.md link after doc reorg

SPEC.md moved to doc/development/SPEC.md in the merged-in commits.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -21,7 +21,7 @@ collide with the per-component `api-v…` / `ui-v…` tags in this monorepo.
 ## [0.9] — 2026-05-06
 
 First public preview of the bundled stack. Everything specified in
-[`SPEC.md`](./SPEC.md) milestones M1–M14 is in place; the `0.9` cut is
+[`SPEC.md`](./doc/development/SPEC.md) milestones M1–M14 is in place; the `0.9` cut is
 the integration milestone where `api` 1.0.0 and `ui` 1.0.0 have been
 shipped together, hardened against the `SEC_REVIEW` findings, and
 verified end-to-end via the demo seed flow.