STYLE: Highlight PR Performance Report signals

[Gaurav Sharma (bewithgaurav)]

Work Item / Issue Reference

AB#44819

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Summary

Improve the deterministic PR Performance Report presentation while preserving its existing measurements, thresholds, and advisory behavior.

• Add explicit success, regression, review, unavailable, and clean verdict headings.
• Summarize signal counts with compact badges.
• Add a task-by-environment signal fingerprint without directional arrows or a spread column.
• Keep exact before/after values in the expandable measured-timings table.
• Rename and emphasize the diagnostic, complete-results, and build-detail sections.
• Run same-repository report workflows from PR code so formatter changes can be validated end to end. Fork pull requests continue to use trusted base-branch code.

This PR is stacked on #795. When merged into that branch, #795 will rerun its performance publisher using this formatter. After #795 reaches main, other pull requests receive the format when they synchronize with main.

Validation

• 118 profiler CI contract tests passed.
• Workflow YAML parsing, Black, Flake8, and diff checks passed.