[codex] Add ranked report clusters

[mbelinky]

Summary

• add report-only action clusters for related maintainability/performance findings
• rank clustered findings by severity/confidence and then cluster size while keeping every original finding in the report
• document the report behavior and add focused reporting tests

Stacking

This is stacked on #55. Until that PR lands, GitHub may show the deslopify commit in this diff as well; after #55 merges, this should collapse to the report-clustering commit.

Audit / hardening

• red-teamed the report layer for misleading rank order and fixed severity to outrank cluster size
• hardened the band-aid pattern matching so ordinary words containing any do not get mislabeled as type-silencing slop
• kept the change report-only: finding IDs, status, triage, storage, and fix commands are unchanged

Validation

• pnpm test src/reporting.test.ts src/workflow.test.ts
• pnpm typecheck
• pnpm build
• pnpm lint
• git diff --check