docs: add RELEASING.md with mempalace-mcp pre-release check

Fulfills the "Optional: release-checklist addition" proposal at the
bottom of MemPalace#1093 (the v3.3.2 release defect where plugin.json referenced
a mempalace-mcp binary that pyproject.toml never declared, so fresh
`pip install` was broken for everyone until messelink's MemPalace#340 was
re-cut as v3.3.3).

New file at docs/RELEASING.md (no existing doc at that path) with a
single pre-release grep:

    grep -rn mempalace-mcp pyproject.toml .claude-plugin .codex-plugin

The original MemPalace#1093 proposal specified `pyproject.toml
.claude-plugin/plugin.json` (2 files). This expands via -rn directory
recursion to also cover `.claude-plugin/.mcp.json` and
`.codex-plugin/plugin.json`, which reference `mempalace-mcp` by name
too — same class of regression through a different surface. Happy to
trim to the narrower 2-file form if preferred; one-line edit.

Shows the concrete expected output so a maintainer running this under
release pressure can eyeball "pass" without mental translation, and
points at MemPalace#340 as the historical fix anchor so "investigate why the
entry is missing" has a diagnostic starting point rather than a dead
end.

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

Author: jphein

docs/RELEASING.md

@@ -0,0 +1,31 @@
+# Releasing MemPalace
+
+## Pre-release checklist
+
+Run from the repo root before cutting a release tag.
+
+### Verify `mempalace-mcp` entry point alignment
+
+The plugin configs reference `mempalace-mcp` as the MCP server command, which
+resolves to a `console_script` entry point declared in `pyproject.toml`. If
+these disagree, `pip install mempalace` ships a plugin config pointing at a
+binary that was never installed — exactly what broke v3.3.2
+([#1093](https://github.com/MemPalace/mempalace/issues/1093)).
+
+```bash
+grep -rn mempalace-mcp pyproject.toml .claude-plugin .codex-plugin
+```
+
+Expected on a healthy `develop` (post-[#340](https://github.com/MemPalace/mempalace/pull/340)):
+
+```
+pyproject.toml:41:mempalace-mcp = "mempalace.mcp_server:main"
+.claude-plugin/plugin.json:12:      "command": "mempalace-mcp"
+.codex-plugin/plugin.json:24:      "command": "mempalace-mcp"
+.claude-plugin/.mcp.json:3:    "command": "mempalace-mcp"
+```
+
+If `pyproject.toml` has no match, **stop** — the entry point is missing and
+any fresh `pip install` will ship a broken plugin config. Investigate whether
+the release branch was cut before
+[#340](https://github.com/MemPalace/mempalace/pull/340) landed on `develop`.