fix: report package-level failures (timeouts, signals) in go test summary

[tmchow]

When go test times out or gets killed by a signal, the JSON stream contains a package-level {"action":"fail"} with no Test field and no FailedBuild field. The parser in filter_go_test_json (go_cmd.rs:447) only handled test-level fails (event.test.is_some()) and build-level fails (event.failed_build.is_some()), so this event fell through silently. The summary saw 0 passes + 0 fails and reported "No tests found."

Before:

$ rtk go test -timeout 3s -run TestHang ./...
Go test: No tests found

After:

$ rtk go test -timeout 3s -run TestHang ./...
Go test: 0 passed, 1 failed in 1 packages
═══════════════════════════════════════

hangtest [FAIL]
  FAIL	hangtest	5.240s

Changes in go_cmd.rs:

• PackageResult struct: added package_failed and package_fail_output fields
• "fail" handler: added else branch for package-level failures that aren't test or build failures
• "output" handler: captures package-level output (timeout messages, signal info) when event.test is None
• Summary: counts package failures in has_failures and displays them with captured output

The exit code was already correct (Go exits 1, rtk propagates it at line 94). Only the summary message was wrong.

Fixes #958

This contribution was developed with AI assistance (Claude Code).

[CLAassistant]

All committers have signed the CLA.

[tmchow]

Why is the GitHub actions being required to sign the CLA?! 🤔

[tmchow]

Rebased on the latest develop. This should be ready for review when you get a chance.

@aeppling are you the right person to ping?

[pszymkowiak]

Tested locally:

• Compilation: OK (release build)
• Unit tests: 4/4 go_cmd tests pass including new test_filter_go_test_timeout_package_fail
• Real timeout test: Confirmed fix works — rtk go test -timeout 3s on a hanging test now correctly reports 0 passed, 1 failed with exit code 1 (was: No tests found exit code 0)
• No regression: Normal passing tests still report correctly

Clean fix, well-scoped, good test coverage.

[tmchow]

thanks @pszymkowiak and @aeppling !