fix(docker): add fastembed-cache-empty placeholder so default bake builds

[SandyChapman]

Summary

A clean checkout cannot run the default Docker build. docker-bake.hcl defaults FASTEMBED_CACHE_CONTEXT to docker/fastembed-cache-empty (added in #384), and Dockerfile.nmp-api consumes it via COPY --from=fastembed-cache .. That directory was never committed — git can't track empty dirs and there was no placeholder file — so the documented local build fails before it starts:

ERROR: failed to get build context fastembed-cache: stat docker/fastembed-cache-empty: no such file or directory
make: *** [docker-load] Error 1

CI's "Build CPU smoke images" job never hits this because ci.yaml overrides FASTEMBED_CACHE_CONTEXT to a ${RUNNER_TEMP}/fastembed-cache dir it mkdirs — so only the committed default path (local dev, make docker-build / docker-load) is broken.

Fix

Commit a tracked placeholder (docker/fastembed-cache-empty/.gitkeep) so the default context exists on checkout. The empty context just means the image downloads the embed model at build time — the existing else-branch in Dockerfile.nmp-api already handles that.

Testing

• Reproduced on a clean main checkout: make docker-load TARGET=docker-cpu failed immediately with the context error above.
• With the directory present, the same command proceeds past context resolution into the image builds.

Notes

Found while doing RCA on an unrelated docker-build status failure. This is a separate, pre-existing bug (default/local builds only); the external CI docker-build gate is unaffected because it overrides the cache context.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Chores
  • Updated build infrastructure to ensure proper directory structure tracking during deployments.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 70ccdca and 2caf4b4.

📒 Files selected for processing (1)

• docker/fastembed-cache-empty/.gitkeep

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📝 Walkthrough

Walkthrough

Adds a .gitkeep placeholder file to docker/fastembed-cache-empty/ so Git tracks the otherwise-empty directory. Inline comments document that docker-bake.hcl and Dockerfile.nmp-api require the directory to exist as a Docker build context.

Changes

Fastembed Cache Directory Placeholder

Layer / File(s)	Summary
Add .gitkeep to fastembed-cache-empty docker/fastembed-cache-empty/.gitkeep	Adds a commented .gitkeep so Git retains the empty directory needed by Docker build context logic in docker-bake.hcl / Dockerfile.nmp-api.

Possibly related PRs

• NVIDIA-NeMo/nemo-platform#384: Introduces the Docker bake and workflow changes that consume docker/fastembed-cache-empty as a build context — the directory this .gitkeep preserves.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	Title accurately describes the main change: adding a .gitkeep file to ensure the fastembed-cache-empty directory exists for default Docker builds.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix-fastembed-empty-context/schapman

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_{Comment @coderabbitai help to get the list of available commands.}

[github-actions]

Suite	Lines Covered	Line Rate	Branch Rate
Unit Tests	21176/27762	76.3%	61.2%
Integration Tests	12216/26531	46.0%	19.5%

[crookedstorm]

Sorry, I failed to commit mine locally! LGTM