Bake mempalace-toolkit wrappers into the image

The scheduler templates in mempalace-toolkit's contrib/ assume
mempalace-session is available inside the container, but the image
never actually installed it. Users following the *-devbox scheduler
docs would silently lose the wrappers on every container recreate,
because the only way to get them was a post-hoc install.sh inside
the container — which lives in the ephemeral layer. The host-side
systemd timer would then fire, docker exec in, and hit
"mempalace-session: command not found".

Caught during runtime validation on 2026-04-30: host-side systemd
unit ran cleanly at 16:15 today, then the container was rebuilt
and recreated, and the wrappers were gone. The rebuild produced
an image that the scheduler template's own documented precondition
did not hold for.

Fix: new Dockerfile block clones mempalace-toolkit at build time
(depth-1) to /opt/mempalace-toolkit/, symlinks bin/mempalace-session
and bin/mempalace-docs into /usr/local/bin/, asserts both respond
to --help before the layer succeeds. Gated by
INSTALL_MEMPALACE_TOOLKIT=true (defaults on, depends on
INSTALL_MEMPALACE=true). Floated ref via MEMPALACE_TOOLKIT_REF=main
for auto-picking-up toolkit updates; override for reproducible
builds once the toolkit starts tagging releases.

Smoke test gains three assertions (mempalace-session --help,
mempalace-docs --help, symlink target check). Resolved-versions
preamble logs the toolkit git short-SHA alongside the other
floated components, so CI logs always record what got baked in.

README gains a Scheduled mining (mempalace-toolkit) subsection
and a build-args row. DOCKER_HUB.md regenerated; sync-check passes.

CHANGELOG.md

@@ -6,6 +6,17 @@ Tags follow `v{opencode_version}[letter]` — bare tag for the first build on a
 
 ---
 
+## v1.14.30b — 2026-04-30
+
+**Bake mempalace-toolkit wrappers into the image.**
+
+- **Fix:** The scheduler templates in [mempalace-toolkit's `contrib/`](https://gitea.jordbo.se/joakimp/mempalace-toolkit/src/branch/main/contrib) assume `mempalace-session` is available inside the container, but the image never actually installed it. Users following the `*-devbox` scheduler docs would silently lose the wrappers on every `docker compose up --force-recreate`, because the only way to get them was a post-hoc `./install.sh --yes` inside the container — which lives in the ephemeral layer. The host-side systemd timer would then fire, `docker exec` in, and hit `mempalace-session: command not found`. Caught during runtime validation on 2026-04-30.
+  - New Dockerfile block clones `mempalace-toolkit` at build time (depth-1) to `/opt/mempalace-toolkit/`, symlinks `bin/mempalace-session` and `bin/mempalace-docs` into `/usr/local/bin/`, and asserts both respond to `--help` before the layer succeeds.
+  - Gated by `ARG INSTALL_MEMPALACE_TOOLKIT=true` (defaults on, depends on `INSTALL_MEMPALACE=true`).
+  - Floated ref via `ARG MEMPALACE_TOOLKIT_REF=main` — override for reproducible builds once the toolkit starts tagging releases.
+- **Tests:** Smoke test gains three toolkit assertions (`mempalace-session --help`, `mempalace-docs --help`, symlink target check). The resolved-versions preamble now logs the toolkit git short-SHA alongside the other floated components.
+- **Docs:** README's MemPalace section gains a `Scheduled mining (mempalace-toolkit)` subsection covering the new wrappers and pointing at `contrib/` for scheduling. New build-args table entry for `INSTALL_MEMPALACE_TOOLKIT`.
+
 ## v1.14.30 — 2026-04-30
 
 Bump opencode to 1.14.30.