(MOT-4299) fix(ci): unbreak cold registry-lane harness e2e builds

[ytallo]

Today's daily (run 31153706659) failed "Test E2E crate" — reproducibly, including on re-run. Two defects compounded:

1. harness/build.rs needs pnpm, but registry mode never sets it up. Since (MOT-4327) feat(harness): live context accounting with a console chip #686 embedded the console UI, compiling harness from scratch runs the UI build. Test E2E crate / Lint E2E crate compile harness (dep of harness-e2e) in every stack mode, but Setup pnpm/Setup Node were gated to stack_mode == 'source' → pnpm not found on PATH panic on the first cold registry-lane build after (MOT-4327) feat(harness): live context accounting with a console chip #686. Fixed by making both steps unconditional.

2. The plain harness-e2e cache key was never saved. save-if: ${{ inputs.coverage }} meant only coverage runs saved, and since (MOT-4299) fix(ci): run daily Harness benchmarks against Registry #735 moved the daily to coverage: false, every registry-lane build compiled and downloaded everything from scratch (which is what exposed defect 1). Fixed with save-if: true.

The e2e crate itself is healthy: 91/91 tests pass warm and cold on stable 1.97.1 (with pnpm on PATH). _harness-integration.yml is not affected — harness-integration has no path dep on harness.

After merge, the next scheduled daily (or a workflow_dispatch) picks this up.

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[github-actions]

skill-check — worker

0 verified, 55 skipped (no docs/).

Layer	Result
structure	✓
vale	✓
ai	✓
render	✓

Four for four. Nicely done.

[coderabbitai]

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Review details

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 6d0aa8c1-26ee-4e29-afbf-6d827cac25c4

📥 Commits

Reviewing files that changed from the base of the PR and between cb4b6ca and be6a71b.

📒 Files selected for processing (1)

• .github/workflows/_harness-e2e.yml

📝 Walkthrough

Walkthrough

The workflow now saves the selected Rust cache key for both coverage and regular builds. The cache save condition is no longer limited to coverage runs.

Changes

Rust cache workflow

Layer / File(s)	Summary
Save Rust caches for all builds .github/workflows/_harness-e2e.yml	The Rust cache step now saves the selected cache key for coverage and regular builds.

Estimated code review effort: 1 (Trivial) | ~3 minutes

Possibly related PRs

• iii-hq/workers#572: This PR also changes Rust cache behavior in _harness-e2e.yml.

Suggested labels: no-ticket

Suggested reviewers: andersonleal

Poem

A rabbit found caches tucked under the hay,
For coverage and builds, they now save away.
No key left behind,
Swift workflows unwind—
Hop, hop, and speed through the day!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
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.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the CI cache fix that prevents cold registry-lane harness e2e builds.

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/mot-4299-harness-e2e-cold-cache

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