feat: add comprehensive Golang language support

Add Go-specific agents, skills, and commands for idiomatic Go development:

Agents:
- go-reviewer: Go code review for concurrency, error handling, security
- go-build-resolver: Fix Go build errors with minimal changes

Skills:
- golang-patterns: Idiomatic Go patterns, best practices, conventions
- golang-testing: TDD, table-driven tests, benchmarks, fuzzing

Commands:
- /go-review: Invoke Go code reviewer
- /go-test: Go TDD workflow with coverage
- /go-build: Fix Go build/vet/lint errors

Also updates README.md to document the new Go support.

commands/go-review.md

@@ -0,0 +1,148 @@
+---
+description: Comprehensive Go code review for idiomatic patterns, concurrency safety, error handling, and security. Invokes the go-reviewer agent.
+---
+
+# Go Code Review
+
+This command invokes the **go-reviewer** agent for comprehensive Go-specific code review.
+
+## What This Command Does
+
+1. **Identify Go Changes**: Find modified `.go` files via `git diff`
+2. **Run Static Analysis**: Execute `go vet`, `staticcheck`, and `golangci-lint`
+3. **Security Scan**: Check for SQL injection, command injection, race conditions
+4. **Concurrency Review**: Analyze goroutine safety, channel usage, mutex patterns
+5. **Idiomatic Go Check**: Verify code follows Go conventions and best practices
+6. **Generate Report**: Categorize issues by severity
+
+## When to Use
+
+Use `/go-review` when:
+- After writing or modifying Go code
+- Before committing Go changes
+- Reviewing pull requests with Go code
+- Onboarding to a new Go codebase
+- Learning idiomatic Go patterns
+
+## Review Categories
+
+### CRITICAL (Must Fix)
+- SQL/Command injection vulnerabilities
+- Race conditions without synchronization
+- Goroutine leaks
+- Hardcoded credentials
+- Unsafe pointer usage
+- Ignored errors in critical paths
+
+### HIGH (Should Fix)
+- Missing error wrapping with context
+- Panic instead of error returns
+- Context not propagated
+- Unbuffered channels causing deadlocks
+- Interface not satisfied errors
+- Missing mutex protection
+
+### MEDIUM (Consider)
+- Non-idiomatic code patterns
+- Missing godoc comments on exports
+- Inefficient string concatenation
+- Slice not preallocated
+- Table-driven tests not used
+
+## Automated Checks Run
+
+```bash
+# Static analysis
+go vet ./...
+
+# Advanced checks (if installed)
+staticcheck ./...
+golangci-lint run
+
+# Race detection
+go build -race ./...
+
+# Security vulnerabilities
+govulncheck ./...
+```
+
+## Example Usage
+
+```
+User: /go-review
+
+Agent:
+# Go Code Review Report
+
+## Files Reviewed
+- internal/handler/user.go (modified)
+- internal/service/auth.go (modified)
+
+## Static Analysis Results
+✓ go vet: No issues
+✓ staticcheck: No issues
+
+## Issues Found
+
+[CRITICAL] Race Condition
+File: internal/service/auth.go:45
+Issue: Shared map accessed without synchronization
+```go
+var cache = map[string]*Session{}  // Concurrent access!
+
+func GetSession(id string) *Session {
+    return cache[id]  // Race condition
+}
+```
+Fix: Use sync.RWMutex or sync.Map
+```go
+var (
+    cache   = map[string]*Session{}
+    cacheMu sync.RWMutex
+)
+
+func GetSession(id string) *Session {
+    cacheMu.RLock()
+    defer cacheMu.RUnlock()
+    return cache[id]
+}
+```
+
+[HIGH] Missing Error Context
+File: internal/handler/user.go:28
+Issue: Error returned without context
+```go
+return err  // No context
+```
+Fix: Wrap with context
+```go
+return fmt.Errorf("get user %s: %w", userID, err)
+```
+
+## Summary
+- CRITICAL: 1
+- HIGH: 1
+- MEDIUM: 0
+
+Recommendation: ❌ Block merge until CRITICAL issue is fixed
+```
+
+## Approval Criteria
+
+| Status | Condition |
+|--------|-----------|
+| ✅ Approve | No CRITICAL or HIGH issues |
+| ⚠️ Warning | Only MEDIUM issues (merge with caution) |
+| ❌ Block | CRITICAL or HIGH issues found |
+
+## Integration with Other Commands
+
+- Use `/go-test` first to ensure tests pass
+- Use `/go-build` if build errors occur
+- Use `/go-review` before committing
+- Use `/code-review` for non-Go specific concerns
+
+## Related
+
+- Agent: `agents/go-reviewer.md`
+- Skills: `skills/golang-patterns/`, `skills/golang-testing/`