Restore IssuesVisualizer redesign reverted by merge 67ce419 and re-apply
Needle triage/test additions. Migrate all remaining screens off the MD3
palette, raw Tailwind colors, gradients and Material Symbols. Remove the
legacy theme block and fonts, drop the duplicate tab strip, rebuild
TelemetryFilters on FilterBar, and document status in AGENTS.md.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>