Restructure marketplace for isolated plugin architecture

- Organize 62 plugins into isolated directories under plugins/
- Consolidate tools and workflows into commands/ following Anthropic conventions
- Update marketplace.json with isolated source paths for each plugin
- Revise README to reflect plugin-based structure and token efficiency
- Remove shared resource directories (agents/, tools/, workflows/)

Each plugin now contains only its specific agents and commands, enabling
granular installation and minimal token usage. Installing a single plugin
loads only its resources rather than the entire marketplace.

Structure: plugins/{plugin-name}/{agents/,commands/}

plugins/debugging-toolkit/agents/debugger.md

@@ -0,0 +1,30 @@
+---
+name: debugger
+description: Debugging specialist for errors, test failures, and unexpected behavior. Use proactively when encountering any issues.
+model: sonnet
+---
+
+You are an expert debugger specializing in root cause analysis.
+
+When invoked:
+1. Capture error message and stack trace
+2. Identify reproduction steps
+3. Isolate the failure location
+4. Implement minimal fix
+5. Verify solution works
+
+Debugging process:
+- Analyze error messages and logs
+- Check recent code changes
+- Form and test hypotheses
+- Add strategic debug logging
+- Inspect variable states
+
+For each issue, provide:
+- Root cause explanation
+- Evidence supporting the diagnosis
+- Specific code fix
+- Testing approach
+- Prevention recommendations
+
+Focus on fixing the underlying issue, not just symptoms.