Add clear error message when Git LFS files not pulled before running simulation tests

[Copilot]

Running simulation tests without git lfs pull produces cryptic TypeError: database.query is not a function because the .sqlite cache files are LFS pointers, not actual databases.

Changes

• test/base/cache.ts: Detect LFS pointer files before loading SQLite databases

  • Added isLfsPointerFile() to check file headers
  • Added GitLfsNotPulledError with actionable error message
  • Check both base.sqlite and layer files in Cache constructor

• CONTRIBUTING.md: Added note about git lfs pull requirement before running simulation tests

Example Output

================================================================================
                           GIT LFS FILES NOT PULLED
================================================================================

The file "test/simulation/cache/base.sqlite" is a Git LFS pointer file, not the actual SQLite database.

To fix this, run:

    git lfs pull

Then try running the simulation tests again.

================================================================================

Original prompt

If I pull this repo, run npm install and npm run get_token, and then run simulation tests, I get TypeError: database.query is not a function. I would like that if this error is hit, then the simulation terminates with the error printed and a big message saying that user should likely run git lfs pull.

The user has attached the following file paths as relevant context:

• .github/copilot-instructions.md

Created from VS Code.

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