build: preserve IPA output on extraction failure

[sunjinshuai]

Description

A failed GitHub artifact extraction leaves a corrupt .ipa in the output directory, or overwrites a previously valid file at the same destination. Save to a temporary file in the destination directory and rename it only after copying and closing succeed. Remove the temporary file on every exit path, matching the existing external-provider download pattern.

Reproduction and root cause

Create an artifact ZIP containing a stored App.ipa entry and flip one payload byte without updating its CRC. extractIPAFromZip returns zip.ErrChecksum, but extractFile has already created/truncated the final destination and copied the corrupt bytes into it. The failed build therefore leaves a fresh *.ipa that later commands can select through ipa.Newest.

The regression test reproduces both cases: no previous destination and an existing destination. Before the fix, both fail because corrupt bytes remain at the final path. After the fix, no new IPA is published and an existing file retains its original bytes.

Related Issue

No existing issue; checked open issues and pull requests for duplicates.

Type of Change

• Bug fix (non-breaking change that fixes an issue)

Checklist

• My code follows the project's coding standards
• Formatting is clean and go vet ./... passes
• I have added tests that prove my fix works
• All new and existing tests pass
• No user-facing documentation change is needed
• My changes don't introduce new warnings

Testing

Passed locally on macOS arm64:

• go test ./internal/build -run TestExtractIPAFromZip -count=1 -v: checksum failures preserve or omit the destination, successful extraction replaces the destination, and a rename failure leaves no temporary file.
• go test -race ./... (Go 1.27.1).
• GOTOOLCHAIN=go1.26.0 go test ./....
• GOTOOLCHAIN=go1.24.0 go test ./internal/build.
• go vet ./..., gofmt -l . (empty), golangci-lint run --timeout=5m (v2.14.0, 0 issues), and git diff --check.
• CLI builds for darwin/arm64, linux/amd64, and windows/amd64.

Cloud builds and live Apple uploads were not run; the failure is reproduced entirely with a local ZIP fixture.

[Interlap01]

Lgtm. Thank you!