perf(raycast): cache registry dirty signatures

[JustYannicc]

What changed

• Replaced List/Grid full-registry dirty snapshots with per-item visible signature caches.
• Added focused regression/metrics coverage for recreated-but-equivalent props and visible field changes.
• Kept the clean branch scoped to current origin/main runtime shapes.

Why

Large registries were still rebuilding snapshot strings for unchanged recreated item props before virtualization could help. This lets unchanged item updates avoid full-registry walks and skip registry version publishes.

Compatibility impact

• List signatures cover id, order, section, title, subtitle, icon, accessories, keywords, detail, quickLook, and action type.
• Grid signatures cover id, order, section title, title, subtitle, content, accessory, keywords, quickLook, and action type.
• Ordering, selection, selected actions, details, filtering keywords, emoji/icon values, and Raycast API-facing item fields remain represented in dirty checks.

How tested

• node scripts/test-registry-dirty-checks.mjs
• node scripts/test-registry-dirty-checks.mjs --report
• LSP diagnostics on touched List/Grid hook files: no errors
• ./node_modules/.bin/tsc -p tsconfig.renderer.json --noEmit reaches TypeScript but fails on existing origin/main errors outside this PR, including App.tsx, CameraExtension.tsx, launcher command model/control types, i18n runtime, and existing raycast-api/settings utility issues.

Stack validation

• Clean PR branch: codex/perf-registry-dirty-checks-pr from origin/main with only this scoped fix.
• Worker branch: codex/perf-registry-dirty-checks from fork/codex/perf-consolidated-integration-stack; validated there with stable-order, emoji-grid virtualization, and grid virtualization scripts before clean-branch adaptation.

[JustYannicc]

Superseded by consolidated upstream PR #555.