Support multiple checkouts with unique mount points

[adityamaru]

Each repository checkout now gets its own isolated sticky disk and mount point to prevent conflicts when multiple repos are checked out in the same workflow.

Changes:

• getMountPoint() returns unique path per repo: /blacksmith-git-mirror-{owner}-{repo}
• setupCache() requests sticky disk with correct repoName from checkout input
• Add repoName and mountPoint to state for post step cleanup
• Add comprehensive tests for multiple checkout scenario

This fixes the issue where second checkout would stacked mount over the first, breaking the first repo's alternates mechanism.

Test plan:

• All existing tests pass (100 tests)
• New unit tests verify path uniqueness and multiple checkout isolation

🤖 Generated with Claude Code

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Note

Isolates Blacksmith git mirrors per repository to avoid conflicts during multiple checkouts.

• Introduces getMountPoint(owner, repo) and updates getMirrorPath to live under /blacksmith-git-mirror/<owner>/<repo>/v1/<owner>-<repo>.git
• setupCache now requests sticky disks with the actual owner/repo and mounts each device at its unique mount point
• Persists repoName, mountPoint, and mirrorPath in state; cleanup unmounts via the stored mount point and commits using the stored repo name
• Adds unit tests validating unique/consistent paths, hyphen collision avoidance, mirror path format, environment detection, and multi-checkout isolation

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