fix(go): report failure when build produces unrecognized error output

[Abhi-DevHub]

Summary

\ilter_go_build_with_exit()\ now reports failure with raw output preserved when \go build\ produces unrecognized non-empty output that doesn't match any known error or progress pattern. Previously, unrecognized lines fell through silently and the filter reported success despite the presence of non-download, non-progress output text.

Problem

\ilter_go_build()\ determined success purely by scanning for known error patterns. When \go build\ failed with an error that didn't match any pattern (e.g. \stat ...: directory not found\ for an invalid package path), the filter swallowed the error and reported success.

A successful \go build\ produces no output (or only \go: downloading ...\ progress lines). Any other unrecognized output indicates an error the filter doesn't understand — it should be passed through, not hidden.

Changes

• \src/cmds/go/go_cmd.rs: Added \has_unrecognized_output()\ helper that detects non-empty, non-download, non-progress, non-header output lines that don't match known error patterns. When \errors.is_empty()\ but unrecognized output exists, \ormat_go_build_failure()\ is called regardless of exit code.
• Added tests for unrecognized error output and download-only success

Test plan

• \cargo clippy --all-targets\ — no warnings
• New test \ est_filter_go_build_unrecognized_error_not_swallowed\ confirms raw error is preserved
• New test \ est_filter_go_build_download_lines_still_success\ confirms download-only output still reports success
• Existing test \ est_filter_go_build_nonzero_exit_never_reports_success\ continues to pass

Fixes #1599

[CLAassistant]

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