refactor!: major directory restructuring and npx support

- Create agents/ directory, move bmad, requirements, development-essentials
- Remove docs/, hooks/, dev-workflow/ directories
- Add npx support via github:cexll/myclaude
- Add bin/cli.js with --update command for installed modules
- Add package.json, skills/README.md, PLUGIN_README.md
- Update all references across config.json, README, marketplace.json
- Change default module from dev to do
- Update CHANGELOG with all 59 tags

BREAKING CHANGE: Directory structure changed, docs/hooks removed

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Co-Authored-By: SWE-Agent.ai <noreply@swe-agent.ai>

PLUGIN_README.md

@@ -0,0 +1,18 @@
+# Plugin System
+
+Claude Code plugins for this repo are defined in `.claude-plugin/marketplace.json`.
+
+## Install
+
+```bash
+/plugin marketplace add cexll/myclaude
+/plugin list
+```
+
+## Available Plugins
+
+- `bmad` - BMAD workflow (`./agents/bmad`)
+- `requirements` - requirements-driven workflow (`./agents/requirements`)
+- `dev-kit` - development essentials (`./agents/development-essentials`)
+- `omo` - orchestration skill (`./skills/omo`)
+- `sparv` - SPARV workflow (`./skills/sparv`)