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.
