ci: write a swift test summary to the job summary

[kieran-osgood-shopify]

Stack Context

Stacked on #595, which writes an .xcresult bundle on CI and uploads it when a Swift job fails.

This PR renders the test results directly on the run page

What?

Read it at Checks → CI → Summary, under the Run Package Tests job. No log expansion, no artifact download.
https://github.com/Shopify/checkout-kit/actions/runs/31108425595?pr=596

Why?

xcode_run already annotates failures at file and line through xcbeautify. That covers a single failure well. It does not scale:

• GitHub caps annotations at 10 errors per step and 50 per job.
• Every Swift test runs in one step, Run Tests.
• Past 10 failures GitHub drops the rest, picks an arbitrary subset, and shows no sign that it truncated.

The job summary has no such cap, so a wide breakage stays legible.

Why package tests only?

xcresultparser only supports test output, not build output

Notes for review

Decision	Reason
--output-format md, not github	The github format emits unbalanced LaTeX ($\textcolor{... never closes) and GitHub renders a math error.
sed 's/\\"/"/g'	The tool escapes its own quotes, which makes style=\"color:red\" malformed HTML.
cat -s	The raw output carries long runs of blank lines.
working-directory: ${{ github.workspace }}	defaults.run.working-directory is platforms/swift, but .xcresults/ sits at the repository root.
shopt -s nullglob	An empty .xcresults/ writes nothing instead of a literal glob.

Verified

The step body ran against the failed bundle from CI run 31104402707
https://github.com/Shopify/checkout-kit/actions/runs/31108425595?pr=596

## ShopifyCheckoutKit-Package

Errors: 0; Warnings: 2; Tests: 883; Failed: 1; Skipped: 0; Execution time = 313.939s

### LockedValueTests (1s)
* 🔴 testGetReturnsInitialValue() (1s)
  * LockedValueTests.swift:8: XCTAssertEqual failed: ("initial") is not equal to (...)

End-to-end CI proof runs through the stacked verification PR #596.

🤖 Generated with Claude Code

[kieran-osgood-shopify]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• DO NOT MERGE: verify xcresult capture in CI #596
• ci: write a swift test summary to the job summary #598 👈 (View in Graphite)
• add artifact upload for swift test failures #595
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[bitrise]

Install this build

Open Tophat, select your target device, then click Install. Links open on the Mac running Tophat.

SDK	Install
Swift	Install with Tophat

Checkout Kit E2E results

Status	Suite	Target	Platform	OS version tag	Device
✅	tests/shared/launch-smoke.yaml	swift	ios	latest	iPhone 15 iOS 27 Beta