ci(go): enforce gofmt for CLI and agent

[bonheur15]

Summary

• format the CLI and agent Go sources with gofmt
• add fail-closed formatting checks to both Go CI workflows
• keep formatting and CI enforcement in separate commits for reviewability

The issue originally named six files. On current develop, gofmt -l apps/cli apps/agent reported nineteen files because additional committed CRLF sources were also non-canonical to gofmt; this PR normalizes all reported files so the new check starts green.

Type of change

• Bug fix
• New feature
• Refactor / cleanup
• Docs
• Infrastructure / CI
• Breaking change

Areas touched

• apps/server (NestJS)
• apps/web (React / Vite)
• apps/agent (Go)
• packages/protocol (shared WebSocket contracts)
• apps/cli (Go)
• .github/workflows

Related issue

Closes #111

Validation

• gofmt -l apps/cli apps/agent — clean
• CLI: go vet ./..., go build ./..., go test ./...
• Agent: go mod tidy plus clean module diff, go vet ./..., go build ./..., go test ./...
• CLI cross-compilation: Linux amd64/arm64, macOS amd64/arm64, Windows amd64
• Agent cross-compilation: Linux amd64/arm64, Windows amd64, macOS arm64
• Both workflow YAML files parsed locally
• Formatting guard negative-path test: an intentionally unformatted Go probe was detected and exited non-zero
• git diff --check upstream/develop...HEAD

Checklist

• Change is focused and stays within the existing module boundaries.
• Formatting-only changes are isolated from CI changes.
• Relevant checks pass locally.
• No application behavior or dependencies changed.

[bonheur15]

Note about the large formatting commit

Most of this diff is caused by gofmt changing Windows-style CRLF line endings to LF. GitHub therefore shows many unchanged lines as removed and added. There are no intentional logic changes.

I formatted all 19 files reported by gofmt; otherwise, the new CI formatting check would fail immediately. The formatting and CI changes are kept in separate commits for easier review.

This should be safe to merge: CLI and Agent tests, builds, vet checks, cross-platform builds, and both GitHub Actions jobs pass. If the maintainers prefer to handle line endings separately, I am happy to adjust the PR.