v1.8.3: mempalace 3.7.1, refreshed skill snapshot, census on PATH

mempalace 3.6.0 -> 3.7.1. Verified against the 3.7.1 source rather than its
changelog, because the risk lands on palaces users cannot reconstruct: legacy
drawers lack the new chunk_total marker and both decision sites trust them, so
no mass re-mine; NORMALIZE_VERSION is 2 in both; chromadb stays <2 so no
index-format migration; no auto-migration exists; logstream.sqlite3 is created
lazily. Downgrade remains possible (3.6.0 has zero references to chunk_total).

Two behaviour changes documented in the CHANGELOG: ALLOW_PEER_WRITER no longer
works on local/chroma palaces, and writer-lock setup failures fail closed.
Neither affects this image's MCP-server-plus-CLI-feeder pattern, which already
serialised on the same lock under 3.6.0 -- the upstream "process-lifetime
single-writer" entry describes tightened escape hatches, not a new lease.

The motivation is the shared central palace: 3.7.1 drops the stale chromadb
SharedSystemClient cache on reconnect (3.6.0 could let a stale in-memory HNSW
segment overwrite a peer's writes, "index count going backwards"), releases the
writer lease on SIGTERM/SIGHUP, and stops treating an interrupted mine as
complete. The fleet primary was upgraded to 3.7.1 and restarted before this tag,
because 3.7.1 refuses writes when the served library drifts and reconnect cannot
clear that. opencode-devbox still pins 3.6.0, so the lockstep is broken until it
cuts its own release.

Vendored mempalace skill snapshot refreshed to skillset 936fed8 (was 63f3bf5).
This closes a gap that had been invisible for two commits: ~/.agents/skills/
mempalace symlinks to the IMAGE-BAKED copy, entrypoint-user.sh creates that link
first, and the skillset deploy never clobbers an existing name -- so in a devbox
container the vendored snapshot always wins and editing skillset alone changes
nothing a container reads. Brings the multi-machine shared-palace section and
the hand-crafted-provenance guard.

pi-global-AGENTS.append.md already carried the three shared-palace damage rules
(a55f636); this tags them into a release.

mempalace-census gets the /usr/local/bin symlink its three siblings have had all
along, plus chmod and a build-time --help smoke check, so RFC-002 Phase A
censuses no longer need an absolute path.

Two new smoke assertions, both confirmed to FAIL against a v1.8.2 container so
they are not tautological: the vendored snapshot must contain the multi-machine
section (a stale manual snapshot is otherwise invisible), and mempalace-census
must be on PATH.

No other pins move: pi stays 0.84.2 (npm latest), pi-atelier v0.8.1, and every
git-ref component was checked against its upstream head and is unchanged.

scripts/smoke-test.sh

@@ -368,6 +368,14 @@ exec_test "settings.json bootstrapped"             'test -f $HOME/.pi/agent/sett
 exec_test "pi-devbox-environment skill linked"     'test -L $HOME/.agents/skills/pi-devbox-environment && test -f $HOME/.agents/skills/pi-devbox-environment/SKILL.md && echo ok'
 exec_test "pi-extensions skill linked (fallback)"  'test -L $HOME/.agents/skills/pi-extensions && test -f $HOME/.agents/skills/pi-extensions/SKILL.md && echo ok'
 exec_test "mempalace skill linked (fallback)"      'test -L $HOME/.agents/skills/mempalace && test -f $HOME/.agents/skills/mempalace/SKILL.md && echo ok'
+# The vendored mempalace snapshot is refreshed MANUALLY per release (see
+# rootfs/usr/local/share/pi-devbox/skills/VENDORED.md). It silently shadows the
+# skillset copy in a devbox container, so a stale snapshot is invisible: assert
+# the multi-machine shared-palace guidance is actually present, not just the file.
+exec_test "mempalace skill snapshot is current"    'grep -q "Shared palace: multiple harnesses" $HOME/.agents/skills/mempalace/SKILL.md && echo ok'
+# mempalace-census gained a /usr/local/bin symlink in v1.8.3; its three siblings
+# had one since they were added, so this asserts the set stays complete.
+exec_test "mempalace-census on PATH"               'command -v mempalace-census >/dev/null && mempalace-census --help >/dev/null && echo ok'
 
 # pi-fork + pi-observational-memory are registered by entrypoint-user.sh via
 # `pi install /opt/<pkg>`, which runs slightly after the keybindings marker.