(MOT-4299) fix(ci): free runner disk before the Harness E2E stack build

[ytallo]

The harness 1.7.1 release (run 30963283418) cleared the fixed candidate gate (#698) and quickstart, then died in Validate candidate in deployed Harness E2E / harness e2e build:

tar: target/harness-e2e-stack.tar.gz: Wrote only 4096 of 10240 bytes

ENOSPC — the registry-mode stack build fills the standard runner's ~14GB free disk. Reproduced identically on a failed-jobs rerun, so it's structural, not runner variance (this is the first harness staged release to reach this stage).

Fix: drop preinstalled toolchains the job never uses (~30GB: dotnet, Android SDK, GHC/ghcup, CodeQL, docker images) as the first step of the shared build job, with a df -h for observability. Benefits both source and registry modes.

Evidence gating context: release_candidate.py requires harness_e2e == success in the same run, and a release rerun uses the tag's workflow snapshot — so this fix can only take effect through a new tag (1.7.2) after merge. Ref #699 for the broader re-run idempotency issue.

Summary by CodeRabbit

• Chores
  • Improved build workflow preparation by freeing disk space before checkout.
  • Added disk capacity reporting to help monitor build environment availability.

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[github-actions]

skill-check — worker

0 verified, 54 skipped (no docs/).

Layer	Result
structure	✓
vale	✓
ai	✓
render	✓

Four for four. Nicely done.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 705fff1e-ff1b-4fa9-9b3e-e85f24c5d9b6

📥 Commits

Reviewing files that changed from the base of the PR and between 6ee021f and 7df9a7e.

📒 Files selected for processing (1)

• .github/workflows/_harness-e2e.yml

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📝 Walkthrough

Walkthrough

The E2E build workflow now frees runner disk space before checkout. It removes unused toolchains, prunes Docker images without failing the job, and reports filesystem usage.

Changes

Workflow maintenance

Layer / File(s)	Summary
Runner disk cleanup .github/workflows/_harness-e2e.yml	The workflow removes unused .NET, Android, GHC, ghcup, and CodeQL directories. It prunes Docker images and reports filesystem usage before checkout.

Estimated code review effort: 1 (Trivial) | ~2 minutes

Suggested reviewers: andersonleal

Poem

A rabbit clears the runner’s floor,
Old toolchains hop out the door.
Docker sheds its dusty load,
Free space lights the build’s brave road.
Checkout starts with room to spare.

🚥 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	The title clearly and concisely describes the CI change to free runner disk space before the Harness E2E stack build.
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.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/e2e-build-disk-space

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