feat: add Cursor IDE support with pre-translated configs

Add complete .cursor/ directory with rules, agents, skills, commands,
and MCP config adapted for Cursor's format. This makes ecc-universal
a truly cross-IDE package supporting Claude Code, Cursor, and OpenCode.

- 27 rule files with YAML frontmatter (description, globs, alwaysApply)
- 13 agent files with full model IDs and readonly flags
- 30 skill directories (identical Agent Skills standard, no translation)
- 31 command files (5 multi-* stubbed for missing codeagent-wrapper)
- MCP config with Cursor env interpolation syntax
- README.md and MIGRATION.md documentation
- install.sh --target cursor flag for project-scoped installation
- package.json updated with .cursor/ in files and cursor keywords

.cursor/commands/update-codemaps.md

@@ -0,0 +1,17 @@
+# Update Codemaps
+
+Analyze the codebase structure and update architecture documentation:
+
+1. Scan all source files for imports, exports, and dependencies
+2. Generate token-lean codemaps in the following format:
+   - codemaps/architecture.md - Overall architecture
+   - codemaps/backend.md - Backend structure
+   - codemaps/frontend.md - Frontend structure
+   - codemaps/data.md - Data models and schemas
+
+3. Calculate diff percentage from previous version
+4. If changes > 30%, request user approval before updating
+5. Add freshness timestamp to each codemap
+6. Save reports to .reports/codemap-diff.txt
+
+Use TypeScript/Node.js for analysis. Focus on high-level structure, not implementation details.