feat: migrate research and index-repo to plugin, delete all slash commands

## Plugin Migration
Added to pm-agent plugin:
- /research: Deep web research with adaptive planning
- /index-repo: Repository index (94% token reduction)
- Total: 3 commands (pm, research, index-repo)

## Slash Commands Deleted
Removed all 27 slash commands from ~/.claude/commands/sc/:
- analyze, brainstorm, build, business-panel, cleanup
- design, document, estimate, explain, git, help
- implement, improve, index, load, pm, reflect
- research, save, select-tool, spawn, spec-panel
- task, test, troubleshoot, workflow

## Architecture Change
Strategy: Minimal start with PM Agent orchestration
- PM Agent = orchestrator (統括コマンダー)
- Task tool (general-purpose, Explore) = execution
- Plugin commands = specialized tasks when needed
- Avoid reinventing the wheel (use official tools first)

## Files Changed
- .claude-plugin/plugin.json: Added research + index-repo
- .claude-plugin/commands/research.md: Copied from slash command
- .claude-plugin/commands/index-repo.md: Copied from slash command
- ~/.claude/commands/sc/: DELETED (all 27 commands)

## Benefits
✅ Minimal footprint (3 commands vs 27)
✅ Plugin-based distribution
✅ Version control
✅ Easy to extend when needed

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

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

.claude-plugin/commands/research.md

@@ -0,0 +1,103 @@
+---
+name: research
+description: Deep web research with adaptive planning and intelligent search
+category: command
+complexity: advanced
+mcp-servers: [tavily, sequential, playwright, serena]
+personas: [deep-research-agent]
+---
+
+# /sc:research - Deep Research Command
+
+> **Context Framework Note**: This command activates comprehensive research capabilities with adaptive planning, multi-hop reasoning, and evidence-based synthesis.
+
+## Triggers
+- Research questions beyond knowledge cutoff
+- Complex research questions
+- Current events and real-time information
+- Academic or technical research requirements
+- Market analysis and competitive intelligence
+
+## Context Trigger Pattern
+```
+/sc:research "[query]" [--depth quick|standard|deep|exhaustive] [--strategy planning|intent|unified]
+```
+
+## Behavioral Flow
+
+### 1. Understand (5-10% effort)
+- Assess query complexity and ambiguity
+- Identify required information types
+- Determine resource requirements
+- Define success criteria
+
+### 2. Plan (10-15% effort)
+- Select planning strategy based on complexity
+- Identify parallelization opportunities
+- Generate research question decomposition
+- Create investigation milestones
+
+### 3. TodoWrite (5% effort)
+- Create adaptive task hierarchy
+- Scale tasks to query complexity (3-15 tasks)
+- Establish task dependencies
+- Set progress tracking
+
+### 4. Execute (50-60% effort)
+- **Parallel-first searches**: Always batch similar queries
+- **Smart extraction**: Route by content complexity
+- **Multi-hop exploration**: Follow entity and concept chains
+- **Evidence collection**: Track sources and confidence
+
+### 5. Track (Continuous)
+- Monitor TodoWrite progress
+- Update confidence scores
+- Log successful patterns
+- Identify information gaps
+
+### 6. Validate (10-15% effort)
+- Verify evidence chains
+- Check source credibility
+- Resolve contradictions
+- Ensure completeness
+
+## Key Patterns
+
+### Parallel Execution
+- Batch all independent searches
+- Run concurrent extractions
+- Only sequential for dependencies
+
+### Evidence Management
+- Track search results
+- Provide clear citations when available
+- Note uncertainties explicitly
+
+### Adaptive Depth
+- **Quick**: Basic search, 1 hop, summary output
+- **Standard**: Extended search, 2-3 hops, structured report
+- **Deep**: Comprehensive search, 3-4 hops, detailed analysis
+- **Exhaustive**: Maximum depth, 5 hops, complete investigation
+
+## MCP Integration
+- **Tavily**: Primary search and extraction engine
+- **Sequential**: Complex reasoning and synthesis
+- **Playwright**: JavaScript-heavy content extraction
+- **Serena**: Research session persistence
+
+## Output Standards
+- Save reports to `docs/research/[topic]_[timestamp].md`
+- Include executive summary
+- Provide confidence levels
+- List all sources with citations
+
+## Examples
+```
+/sc:research "latest developments in quantum computing 2024"
+/sc:research "competitive analysis of AI coding assistants" --depth deep
+/sc:research "best practices for distributed systems" --strategy unified
+```
+
+## Boundaries
+**Will**: Current information, intelligent search, evidence-based analysis
+**Won't**: Make claims without sources, skip validation, access restricted content