refactor: replace Code Index MCP with native CCW CodexLens

Migrate all Code Index MCP references to CCW's built-in CodexLens tool:
- Update context-search-agent with codex_lens API calls
- Update test-context-search-agent with new search patterns
- Update memory/load command file discovery reference
- Update context-gather and task-generate-tdd MCP capabilities
- Update INSTALL docs to reflect CodexLens as built-in feature
- Sync all mirrored files in skills/command-guide/reference/

Old API (mcp__code-index__*) → New API (mcp__ccw-tools__codex_lens)

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.claude/commands/workflow/tools/task-generate-tdd.md

@@ -113,7 +113,7 @@ Phase 2: Agent Execution (Document Generation)
     // Existing test patterns and coverage analysis
   },
   "mcp_capabilities": {
-    "code_index": true,
+    "codex_lens": true,
     "exa_code": true,
     "exa_web": true
   }
@@ -338,7 +338,7 @@ Generate all three documents and report completion status:
 - TDD cycles configured: N cycles with quantified test cases
 - Artifacts integrated: synthesis-spec, guidance-specification, N role analyses
 - Test context integrated: existing patterns and coverage
-- MCP enhancements: code-index, exa-research
+- MCP enhancements: CodexLens, exa-research
 - Session ready for TDD execution: /workflow:execute
 `
 )