cmd: add init-plugin command for plugin scaffolding [minor-release]

[Tanq16]

What

Adds a claudex init-plugin <name> command that scaffolds a Claude Code plugin directory, so starting a new plugin doesn't mean hand-creating the tree and remembering the manifest shape.

Running claudex init-plugin my-plugin creates ./my-plugin/:

my-plugin/
├── .claude-plugin/
│   └── plugin.json      {"name": "my-plugin", "version": "0.0.1"}
├── skills/.gitkeep
├── agents/.gitkeep
├── hooks/.gitkeep
├── output-styles/.gitkeep
├── .mcp.json            {"mcpServers": {}}
├── .lsp.json            {}
└── settings.json        {}

Details

• One required positional arg <name> (cobra.ExactArgs(1)) — becomes both the directory name and the plugin.json "name".
• version is hardcoded to 0.0.1.
• Empty component directories carry a .gitkeep so they survive version control; config files are written as minimal valid JSON skeletons.
• .lsp.json is a bare {} — a standalone .lsp.json is a language→config map, so the empty form has no lspServers wrapper (unlike .mcp.json, which keeps mcpServers). Confirmed against the plugins reference.
• Refuses to overwrite an existing ./<name> directory (exits non-zero).
• Output goes through the utils printer, so --for-ai emits the plain [OK] path.

Verification

• go build ./..., go vet ./..., gofmt -l all clean.
• Exercised end-to-end: generated tree matches the layout above with 0-byte .gitkeep files and correct JSON; rerun on an existing dir refuses with exit 1; --for-ai prints the plain path.

🤖 Generated with Claude Code