fix: make cgroup acceptance test robust to runc scope naming

[mkocher]

This is fixing CI after #219. Oddly there are some green builds with #219 that we can't explain, but the majority of them are red. They're red because the test server can't find the container to check if limits have been applied correctly.

The CgroupLimits test-server handler hardcoded the runc default scope name (runc-bpm-.scope). Since the cgroup-v2-aware CgroupsPath fix (f8e0e29), runc derives the scope name from the self cgroup path, so it varies by environment (e.g. docker-bpm-bpm-.scope), causing test-acceptance-noble to fail when cgroup v2 is delegated into the BOSH VM.

findCgroupDir now matches on the bpm container ID, accepting both the cgroupfs leaf directory (named exactly containerID) and any systemd scope ending in -.scope. The container ID is built via jobid.Encode to stay in sync with config.BPMConfig.ContainerID. Adds unit tests covering the legacy, cgroup-v2-aware, cgroupfs, named-process, and negative cases.

[coderabbitai]

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: 155685fb-699c-41d2-94b5-230bfcf6eb7b

📥 Commits

Reviewing files that changed from the base of the PR and between 4a18d79 and c14b36d.

📒 Files selected for processing (2)

• src/bpm/acceptance/fixtures/test-server/handlers/cgroup_limits.go
• src/bpm/acceptance/fixtures/test-server/handlers/cgroup_limits_test.go

Walkthrough

The cgroup-limits test server handler is updated to derive a BPM container ID using jobid.Encode from the job name and optional process name, replacing the previous direct construction of a systemd runc scope name string. findCgroupDir is rewritten to walk the cgroup filesystem and match directories either named exactly as the container ID (cgroupfs mode) or whose names end with -<containerID>.scope (systemd mode, covering legacy and cgroup-v2-aware patterns). Error messages now reference the container ID. A new Ginkgo/Gomega test file is added that covers all naming conventions—legacy systemd, cgroup-v2 systemd, cgroupfs, named-process encoding—plus negative cases for missing and partial-match directories.

Suggested reviewers

• mariash
• a-hassanin

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'fix: make cgroup acceptance test robust to runc scope naming' clearly and accurately summarizes the main change: updating the cgroup test handler to be robust to varying runc scope naming conventions rather than relying on a hardcoded pattern.
Description check	✅ Passed	The pull request description provides relevant context explaining the CI failures from PR #219, the root cause (hardcoded runc scope name), the environmental variation issue, and details the solution implemented.
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-cgroup-acceptance-test-scope-naming

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@src/bpm/acceptance/fixtures/test-server/handlers/cgroup_limits_test.go`:
- Line 42: The os.RemoveAll(root) call on line 42 is not checking the returned
error, which causes the errcheck linter to fail. Wrap the os.RemoveAll(root)
call in a Gomega assertion (using Expect) to check that the error is nil,
ensuring the linter passes and proper error handling is in place for the cleanup
operation.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: 86ef7ed9-1213-4d2a-925b-8afa1a8dc0ac

📥 Commits

Reviewing files that changed from the base of the PR and between 0d02843 and 4a18d79.

📒 Files selected for processing (2)

• src/bpm/acceptance/fixtures/test-server/handlers/cgroup_limits.go
• src/bpm/acceptance/fixtures/test-server/handlers/cgroup_limits_test.go

[aramprice]

nit: prefer fmt.Sprintf()