release: v2.5.0 — external/shared MemPalace + validate.yml base-change fixes

Promotes the Unreleased block to v2.5.0. Bundled contents:
- feat: optional shared/external MemPalace — generate-config.py registers a remote
  MCP endpoint when MEMPALACE_REMOTE_URL is set; adds docker-compose.mempalace.yml.
- fix: validate.yml false-red on base-changing commits (skip validate-base/omos via
  base_changed) + rootfs/ base-input detector regex.
opencode stays 1.17.13 (== npm latest). Base rebuilds (rootfs/generate-config.py
changed); mempalace-toolkit clone advances to main HEAD (external-transport bridge).

CHANGELOG.md

@@ -6,7 +6,17 @@ Tags follow **independent semver** (since `v2.0.0`) — they version *this image
 
 ---
 
-## Unreleased
+## v2.5.0 — 2026-07-02
+
+Minor release. Headline: **optional shared/external MemPalace** —
+`generate-config.py` can now register mempalace as a `remote` MCP endpoint
+(`MEMPALACE_REMOTE_URL`, optional `MEMPALACE_REMOTE_TOKEN` → Bearer) so one
+palace can serve pi + opencode + native, instead of a per-container local
+server; adds `docker-compose.mempalace.yml` for the shared server. Also fixes a
+`validate.yml` false-red on base-changing commits (skips variant validation and
+corrects the `rootfs/` base-input detector regex). opencode stays `1.17.13`; the
+base image rebuilds (`rootfs/…/generate-config.py` changed), so the new config
+generator lands in `base-<hash>`.
 
 ### Added