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/rules/common-hooks.md

@@ -0,0 +1,35 @@
+---
+description: "Hook system guidelines and TodoWrite best practices"
+alwaysApply: true
+---
+
+# Hooks System
+
+## Hook Types
+
+- **PreToolUse**: Before tool execution (validation, parameter modification)
+- **PostToolUse**: After tool execution (auto-format, checks)
+- **Stop**: When session ends (final verification)
+
+## Auto-Accept Permissions
+
+Use with caution:
+- Enable for trusted, well-defined plans
+- Disable for exploratory work
+- Never use dangerously-skip-permissions flag
+- Configure `allowedTools` in `~/.claude.json` instead
+
+## TodoWrite Best Practices
+
+Use TodoWrite tool to:
+- Track progress on multi-step tasks
+- Verify understanding of instructions
+- Enable real-time steering
+- Show granular implementation steps
+
+Todo list reveals:
+- Out of order steps
+- Missing items
+- Extra unnecessary items
+- Wrong granularity
+- Misinterpreted requirements