chore(plugin): clean up plugin manifests

- Remove no-op `"hooks": {}` from .claude-plugin/plugin.json (auto-discovery from hooks/hooks.json picks up the SessionStart hook).
- Remove redundant `version` from marketplace.json plugin entry; plugin.json is the source of truth per the spec.
- Sync description / longDescription across .claude-plugin and .codex-plugin manifests so all surfaces show the same copy.

.claude-plugin/marketplace.json

@@ -10,8 +10,7 @@
   "plugins": [
     {
       "name": "last30days",
-      "description": "Research any topic across Reddit, X, YouTube, TikTok, Instagram, HN, Polymarket, GitHub, and 5+ more sources.",
-      "version": "3.1.1",
+      "description": "Research any topic across Reddit, X, YouTube, TikTok, Instagram, Hacker News, Polymarket, GitHub, and 5+ more sources. AI agent scores by upvotes, likes, and real money - not editors.",
       "author": {
         "name": "Matt Van Horn",
         "url": "https://github.com/mvanhorn"