CLI Phase 0: bootstrap tracebloc/cli repo + Go module + CI

[saadqbal]

Part of #147. Phase 0 of 5. Estimated ~2 days.

Scope

• Create new repo tracebloc/cli
• Initialize Go module (go.mod, go 1.22)
• Set up command tree skeleton with cobra: cmd/tracebloc/main.go + internal/cli/root.go
• License (Apache-2.0), README skeleton, CONTRIBUTING, CODEOWNERS, .gitignore
• Mirror the kanban-routing + FR-gate workflows from tracebloc/client (.github/workflows/add-to-kanban.yml, fr-gate-caller.yml, fr-pass-comment-caller.yml, set-pr-status.yml, advance-deploy-env.yml, wip-limit-check.yml)
• CI workflow (build.yml): go vet, go test, golangci-lint, build for all 5 platforms (linux amd64/arm64, darwin amd64/arm64, windows amd64), upload binaries as workflow artifacts
• Implement tracebloc version (prints semver + git sha + build time, populated via -ldflags at build)
• Implement tracebloc completion {bash|zsh|fish|powershell} (cobra gives this for free)
• Smoke test in CI: build binary, run tracebloc version, assert non-empty output

Acceptance criteria

• git clone tracebloc/cli && cd cli && go build ./cmd/tracebloc && ./tracebloc version prints something sensible
• CI green on first PR
• Cross-platform binaries downloadable from the CI workflow's artifact tab
• README mentions the epic + roadmap to v0.1

Closes / blocks

• Blocks Epic: tracebloc CLI — tracebloc dataset push for one-command ingestion #147 Phase 1 (Phase 1 needs the repo + module structure)