[narendasan]

Captures the build recovery flow that isn't covered in docsrc/getting_started/installation.rst: failure-mode -> fix mapping (libtorch ABI undefined-symbol errors, stale _C.so, the four artifacts to remove for a clean rebuild), the background-build polling pattern, and the TMPDIR workaround for shared-host engine-cache permission collisions. Anchors the build/ gitignore pattern to the repo root so the skill directory (.claude/skills/build/) isn't silently ignored.

Description

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Fixes # (issue)

Type of change

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• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project (You can use the linters)
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas and hacks
• I have made corresponding changes to the documentation
• I have added tests to verify my fix or my feature
• New and existing unit tests pass locally with my changes
• I have added the relevant labels to my PR in so that relevant reviewers are notified