Initial implementation of pluginctl CLI tool

- Add comprehensive info command with plugin manifest parsing -
Implement global --plugin-path flag and PLUGINCTL_PLUGIN_PATH env var -
Add full test suite with fixtures for various plugin configurations -
Set up build system with Makefile, goreleaser, and golangci-lint -
Include development tools with pinned versions for reproducible builds

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

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

testdata/minimal_plugin.json

@@ -0,0 +1,5 @@
+{
+    "id": "com.example.minimal",
+    "name": "Minimal Test Plugin",
+    "version": "1.0.0"
+}