fix: restructure plugin system for Claude Code compatibility

Major fixes for Claude Code plugin installation:

1. Moved marketplace.json to repo root (.claude-plugin/)
   - Fixes known bug #11243, #11278 with local marketplace path resolution
   - Claude Code uses marketplace.json file path as base, not directory

2. Simplified plugin.json manifests
   - Removed commands/agents/skills directory declarations
   - Claude Code auto-discovers these from standard directories
   - Specifying directories caused "must end with .md" validation errors

3. Cleaned command frontmatter
   - Removed non-standard fields (name, agent, arguments)
   - Only description field is valid in command frontmatter

4. Removed deprecated claude-plugin-developer skill
   - Skill was never properly integrated
   - Removed from repo and all documentation references

All three plugins now validate successfully:
- projman: Sprint planning with Gitea/Wiki.js
- cmdb-assistant: NetBox CMDB integration
- project-hygiene: Post-task cleanup hooks

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.claude-plugin/marketplace.json

@@ -0,0 +1,29 @@
+{
+  "name": "projman-marketplace",
+  "version": "1.0.0",
+  "description": "Project management plugins with Gitea, Wiki.js, and NetBox integrations",
+  "owner": {
+    "name": "Bandit Labs",
+    "email": "dev@banditlabs.io"
+  },
+  "plugins": [
+    {
+      "name": "projman",
+      "version": "0.1.0",
+      "description": "Sprint planning and project management with Gitea and Wiki.js integration",
+      "source": "./plugins/projman"
+    },
+    {
+      "name": "project-hygiene",
+      "version": "0.1.0",
+      "description": "Post-task cleanup hook that removes temp files and manages orphaned files",
+      "source": "./plugins/project-hygiene"
+    },
+    {
+      "name": "cmdb-assistant",
+      "version": "1.0.0",
+      "description": "NetBox CMDB integration for infrastructure management",
+      "source": "./plugins/cmdb-assistant"
+    }
+  ]
+}