Add CI-native JUnit and TAP test reports

Summary

Add structured per-test results and built-in JUnit XML and TAP report formats to GocciaTestRunner.

Why

CI systems and editor tooling need standard machine-readable test reports. The current JSON envelope is useful for GocciaScript tooling but lacks the per-test records required to produce portable CI reports.

Current behavior

The testing library returns aggregate counts, a duration, suite names, and failed-test strings. The runner emits human output or a JSON envelope containing file-level aggregates; it has no normalized result for each test case and no JUnit or TAP output.

Expected behavior

• Record each test case's file, suite ancestry, full name, status, duration, and failure details in a normalized result model.
• Emit valid JUnit XML and TAP with explicit stdout/file destinations.
• Represent skipped, todo, failed, timed-out, and load-error outcomes without losing existing diagnostics.
• Keep exit status based on the test result rather than the selected report format.
• Preserve existing human, JSON, and compact-JSON behavior.
• Produce deterministic reports for serial and --jobs runs in interpreter and bytecode modes.

Scope notes

• A custom reporter plugin API, HTML reports, browser UI, and provider-specific annotation APIs are out of scope.
• Attempt records from future retry/repeat support should extend the normalized model rather than be flattened into strings.
• Coverage formats and thresholds remain separate from test-result reporting.

Start by locating GocciaTestRunner and the existing human and JSON output paths, then compare serial and --jobs execution in interpreter and bytecode modes. Done means normalized per-test records, deterministic JUnit XML and TAP outputs, preserved existing formats and diagnostics, and exit status based on test results.