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/golang-hooks.md

@@ -0,0 +1,17 @@
+---
+description: "Go hooks: gofmt/goimports auto-format, go vet, staticcheck"
+globs: ["**/*.go"]
+alwaysApply: false
+---
+
+# Go Hooks
+
+> This file extends [common/hooks.md](../common/hooks.md) with Go specific content.
+
+## PostToolUse Hooks
+
+Configure in `~/.claude/settings.json`:
+
+- **gofmt/goimports**: Auto-format `.go` files after edit
+- **go vet**: Run static analysis after editing `.go` files
+- **staticcheck**: Run extended static checks on modified packages