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/build-fix.md

@@ -0,0 +1,29 @@
+# Build and Fix
+
+Incrementally fix TypeScript and build errors:
+
+1. Run build: npm run build or pnpm build
+
+2. Parse error output:
+   - Group by file
+   - Sort by severity
+
+3. For each error:
+   - Show error context (5 lines before/after)
+   - Explain the issue
+   - Propose fix
+   - Apply fix
+   - Re-run build
+   - Verify error resolved
+
+4. Stop if:
+   - Fix introduces new errors
+   - Same error persists after 3 attempts
+   - User requests pause
+
+5. Show summary:
+   - Errors fixed
+   - Errors remaining
+   - New errors introduced
+
+Fix one error at a time for safety!