fix: clarify invalid container root errors

[efegokdemir]

Summary

The update-ldcache hook used one error branch for OCI root lookup failures and invalid root values, producing a misleading <nil> suffix for empty or / roots. The cases are now split, lookup failures preserve their cause, and invalid roots are reported explicitly.

Changes

• Keep validation inline in run, per maintainer feedback.
• Preserve the underlying GetContainerRoot() failure with %w.
• Report empty or / roots as explicit invalid-root errors.
• Remove the no-longer-needed added test file.
• Squash contributor work into one cryptographically signed commit.

Validation

• gofmt -w cmd/nvidia-cdi-hook/update-ldcache/update-ldcache.go
• go test ./cmd/nvidia-cdi-hook/update-ldcache — passed
• go vet ./cmd/nvidia-cdi-hook/update-ldcache — passed
• go build ./cmd/nvidia-cdi-hook/update-ldcache — passed
• git diff --check — passed

The PR has one contributor commit, GitHub reports it as Verified, and the Golang and CodeQL checks are green.

Issue

Fixes #2115

[copy-pr-bot]

This pull request requires additional validation before any workflows can run on NVIDIA's runners.

Pull request vetters can view their responsibilities here.

Contributors can view more details about this message here.

[henry118]

@efegokdemir Also can you please cryptographically sign the commits? thanks

[efegokdemir]

Inlined the container-root lookup error and invalid-root checks directly in run and removed the helper abstraction. I rewrote the two contributor commits with the configured GitHub-linked SSH signing key and force-pushed with --force-with-lease; GitHub reports both replacement commits as verified.

[efegokdemir]

@henry118 The requested cleanup is on the existing branch: the helper was inlined, the extra test file was removed, and the contributor commits were rewritten with verified cryptographic signatures. DCO is passing and the focused update-ldcache tests were run. Please re-review when available.

[henry118]

/ok to test c06d8ee

[coveralls]

Coverage Report for CI Build 36918093826

Warning

Build has drifted: This PR's base is out of sync with its target branch, so coverage data may include unrelated changes.
Quick fix: rebase this PR. Learn more →

Coverage decreased (-0.01%) to 44.26%

Details

• Coverage decreased (-0.01%) from the base build.
• Patch coverage: 5 uncovered changes across 1 file (0 of 5 lines covered, 0.0%).
• 1 coverage regression across 1 file.

Uncovered Changes

File	Changed	Covered	%
cmd/nvidia-cdi-hook/update-ldcache/update-ldcache.go	5	0	0.0%

Coverage Regressions

1 previously-covered line in 1 file lost coverage.

File	Lines Losing Coverage	Coverage
cmd/nvidia-cdi-hook/update-ldcache/update-ldcache.go	1	0.0%

---

Coverage Stats

Relevant Lines:	13554
Covered Lines:	5999
Line Coverage:	44.26%
Coverage Strength:	0.44 hits per line

---

💛 - Coveralls