ci: Update Blacksmith checkout to v1.5.0

[shortstacked]

Summary

Update all 24 existing useblacksmith/checkout references to the immutable v1.5.0 commit.

This release improves shallow fetch performance when a hydrated mirror is attached. It prevents Git from walking the complete mirror object graph during shallow fetch negotiation.

How to test

1. Run actionlint on the changed workflow files.
2. Run a Docker build workflow on a Blacksmith runner.
3. Compare the checkout fetch duration with the previous run.

Local validation:

• actionlint passed for all changed workflow files.
• git diff --check passed.
• The pre-commit actionlint_check hook passed.

Related Linear tickets, Github issues, and Community forum posts

• Upstream fix: Shallow fetch: negotiate from mirror tips with alternate ref discovery off useblacksmith/checkout#50
• Baseline job: https://github.com/n8n-io/n8n/actions/runs/33901561845/job/101127488503

Review / Merge checklist

• I have seen this code, I have run this code, and I take responsibility for this code.
• PR title and summary are descriptive.
• Docs are not required for this dependency update.
• The upstream action includes regression tests.
• Add a backport label if this update needs a backport.

🤖 PR Summary generated by AI

[n8n-assistant]

PR review overview

Based on ownership of the 17 changed files in this PR:

Ownership	Files owned	Share	Source code	Test files	Misc
@n8n-io/qa-dx	17	100%	+24 / -24	+0 / -0	+0 / -0
Total	17	100%	+24 / -24	+0 / -0	+0 / -0

Required reviews

Some changed files have a required owner in OWNERS. A member of each of these teams must approve this PR before it can merge:

Team	Files
@n8n-io/qa-dx	17

Request a review from the team — GitHub assigns reviewers according to the team's review settings. The Auto-assign reviewers label does this for all owning teams.

[cubic-dev-ai]

No issues found across 17 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

<sub>Shadow auto-approve: would auto-approve. Pins all useblacksmith/checkout references to v1.5.0, a routine CI dependency update improving shallow fetch performance. No behavioral changes beyond the action version; bounded and clearly beneficial.

Re-trigger cubic</sub>

[github-actions]

Instance AI Discovery Eval ✅

Branch: ci-update-blacksmith-checkout-v1-5-0 · Commit: 58a1e9affc5ea9cd34479ee4d57a07b604cdaf8a

Eval output

$ tsx evaluations/discovery/cli.ts --trials 3 --fail-on-zero-pass
Running 17 discovery scenario(s) × 3 trial(s) (model: anthropic/claude-sonnet-4-6, concurrency: 3).

▸ config-evals-skill-loading ... (node:4907) [DEP0205] DeprecationWarning: `module.register()` is deprecated. Use `module.registerHooks()` instead.
(Use `node --trace-deprecation ...` to show where the warning was created)
✓ 3/3 passed (100%)
▸ data-table-natural-list-skill-loading ... ✓ 3/3 passed (100%)
▸ data-table-skill-loading ... ✓ 3/3 passed (100%)
▸ data-table-workflow-skill-loading ... ✓ 3/3 passed (100%)
▸ google-oauth-credential-setup ... ✓ 3/3 passed (100%)
▸ http-node-config-no-browser ... ✓ 3/3 passed (100%)
▸ mcp-broken-connection-reconnect ... ✓ 3/3 passed (100%)
▸ mcp-connect-unconnected-service ... ✓ 3/3 passed (100%)
▸ mcp-declined-tool-call-no-reconnect ... ✓ 2/3 passed (67%)
▸ mcp-no-registry-match ... ✓ 3/3 passed (100%)
▸ mcp-not-offered-for-workflow-build ... ✓ 3/3 passed (100%)
▸ mcp-uses-connected-server-tools ... ✓ 3/3 passed (100%)
▸ oauth-with-computer-use-disabled ... ✓ 3/3 passed (100%)
▸ screenshot-dashboard ... ✓ 3/3 passed (100%)
▸ slack-oauth-credential-setup ... ✓ 3/3 passed (100%)
▸ workflow-builder-no-agent-builder-leak ... ✓ 3/3 passed (100%)
▸ workflow-builder-no-credential-ask ... ✓ 3/3 passed (100%)

=== Summary ===
Scenarios: 17/17 above threshold (67%)
Trials: 50/51 passed (98%)
Total time: 1566.2s