Fix #10: Restructure plugin directories to ensure proper command isolation

- Create separate directories for each plugin (requirements-driven-workflow/, bmad-agile-workflow/, development-essentials/, advanced-ai-agents/)
- Update marketplace.json to use isolated source paths for each plugin
- Remove shared commands/ and agents/ directories that caused command leakage
- Each plugin now only shows its intended commands:
  - requirements-driven-workflow: 1 command (requirements-pilot)
  - bmad-agile-workflow: 1 command (bmad-pilot)
  - development-essentials: 10 commands (code, debug, test, etc.)
  - advanced-ai-agents: 0 commands (agents only)

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

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

development-essentials/commands/think.md

@@ -0,0 +1,29 @@
+## Usage
+
+`/project:think <TASK_DESCRIPTION>`
+
+## Context
+
+- Task description: $ARGUMENTS
+- Relevant code or files will be referenced ad-hoc using @ file syntax.
+
+## Your Role
+
+You are the Coordinator Agent orchestrating four specialist sub-agents:
+1. Architect Agent – designs high-level approach.
+2. Research Agent – gathers external knowledge and precedent.
+3. Coder Agent – writes or edits code.
+4. Tester Agent – proposes tests and validation strategy.
+
+## Process
+
+1. Think step-by-step, laying out assumptions and unknowns.
+2. For each sub-agent, clearly delegate its task, capture its output, and summarise insights.
+3. Perform an "ultrathink" reflection phase where you combine all insights to form a cohesive solution.
+4. If gaps remain, iterate (spawn sub-agents again) until confident.
+
+## Output Format
+
+1. **Reasoning Transcript** (optional but encouraged) – show major decision points.
+2. **Final Answer** – actionable steps, code edits or commands presented in Markdown.
+3. **Next Actions** – bullet list of follow-up items for the team (if any).