Emit CTRF output on test when --json is passed

[jviotti]

See: #589
Signed-off-by: Juan Cruz Viotti [email protected]

[augmentcode]

🤖 Augment PR Summary

Summary: This PR extends the test command to emit results in CTRF (Common Test Report Format) when --json/-j is provided, enabling easier integration with CI dashboards and standardized reporting.

Changes:

• Refactors src/command_test.cc into reusable helpers (suite parsing, text reporting, CTRF reporting)
• Implements CTRF JSON report generation (tool metadata, summary counts, per-test entries with duration/file/line)
• Updates CLI help text and testing documentation to mention CTRF output via --json
• Adds new UNIX shell tests that validate CTRF output against a vendored CTRF JSON Schema and compare normalized output
• Adjusts an existing test to expect clean JSON error output when --json is used
• Vendors CTRF schema artifacts under vendor/ctrf/ and registers the CTRF dependency

Technical Notes: The CTRF output is printed via sourcemeta::core::prettify and failures still use exit code 2 to distinguish test failures from execution errors.

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[augmentcode]

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