fix: remove duplicate /last30days command wrapper (#461) (#462)

* fix: remove duplicate command wrapper so plugin exposes only the skill (#461)

The plugin shipped both commands/last30days.md and the skill under the
same name, so /last30 surfaced two `last30days` entries with two
different descriptions. Remove the wrapper; the skill already carries
its own argument-hint, so the /last30days <topic> picker UX is unchanged.

Also corrects the README install note that claimed Claude Code dedupes
the slash command across install methods (it does not), and bumps
3.3.0 -> 3.3.1 across plugin.json, marketplace.json, gemini-extension.json,
and SKILL.md.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix: bump pyproject.toml version to 3.3.1 (manifest contract)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* chore: update uv.lock for 3.3.1 version bump

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Matt Van Horn <455140+mvanhorn@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

README.md

@@ -189,7 +189,7 @@ If you'd rather use the agent-skills install path on Claude Code, that's also su
 npx skills add mvanhorn/last30days-skill -g -a claude-code
 ```
 
-The native plugin and the `npx skills` install can coexist; Claude Code dedupes the slash command.
+The native plugin and the `npx skills` install can coexist. Note that Claude Code does not dedupe across install methods: if you have both the marketplace plugin and the `npx skills` copy active, `/last30days` will show two entries. Use one install method per machine.
 
 ### Codex, Cursor, Copilot, Gemini CLI, and other Agent Skills hosts