Add repository CI workflow

[jsibbison-square]

Adds GitHub Actions verification for the standalone CLI introduced in #2 (merged). This PR now targets main.

The workflow bootstraps the Hermit-managed toolchain from public packages and runs just ci on pull requests, pushes to main, and manual dispatches. It includes the auth crate in workspace tests and Clippy, smoke-checks both release binaries, and runs the isolated Docker acceptance harness against its local mock service.

Validation: Hermit just ci passed 309 tests on macOS. GitHub Actions passed 307 tests on Linux, release smoke checks and Docker mock acceptance. The two extra macOS tests cover platform-specific auth behavior.

[github-advanced-security]

You are seeing this message because GitHub Code Scanning has recently been set up for this repository, or this pull request contains the workflow file for the Code Scanning tool.

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• The 'Security' tab will display more code scanning analysis results (e.g., for the default branch).
• Depending on your configuration and choice of analysis tool, future pull requests will be annotated with code scanning analysis results.
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For more information about GitHub Code Scanning, check out the documentation.

[nathan-thillairajah]

🤖 Updated this stack to include #2 at f7a9ac2, preserving its CODEOWNERS update. Head 5e266e6 adds workspace-wide auth tests and Clippy, release bl version/help smoke checks, and the actual mock Docker acceptance run.

CI passed on this head: 307 tests on Linux, release smoke, and Docker mock acceptance. Local macOS just ci also passed all 309 tests (two additional macOS-specific auth tests). Semgrep, zizmor and DCO pass.

This PR remains based on #2. Merge #2 first after its required review and Nathan's confirmation, then retarget this PR to main and recheck the diff/checks. Nothing merged.

[nathan-thillairajah]

🤖 Retargeted to main after #2 merged. Refreshed the branch at 3577c4a to account for the squash merge; its file tree is identical to the previously validated 5e266e6, and the PR now shows only the six intended CI/toolchain files.

Fresh CI passed, including Docker mock acceptance. Semgrep, zizmor and DCO also pass. Targeting main now requires reviewer approval. No merge performed.