perf(list): stabilize item registry order

[JustYannicc]

What changed

• Store each List.Item registry order in a ref, matching the existing Grid item pattern, so selection-context renders do not allocate a new order.
• Add scripts/test-list-registry-stable-order.mjs as both a reportable churn measurement and a regression guard.

Why

• ListItemComponent consumes SelectedItemActionsContext so selected item changes re-render the hidden List item tree.
• The previous render-time ++itemOrderCounter participated in the registration layout-effect dependencies, causing every item to unregister/register when selection changed.
• Keeping order stable removes the registry churn while preserving selected item action rendering inside the item context tree.

Compatibility impact

• Behavior-preserving for selection, actions, details, empty views, grouping, keyboard controls, and ordering.
• No new UI strings or i18n changes.
• Small local type annotation on the accessory mapper only removes an implicit-any diagnostic in the touched file.

How tested

• Before metric: node scripts/test-list-registry-stable-order.mjs --report on pre-change code with 1,000 items and 25 selection moves reported orderMode=render-counter, layoutEffectRestarts=25000, registryMutationsOnSelection=50000, registryVersionUpdatesOnSelection=25.
• After metric: the same report now shows orderMode=stable-ref, layoutEffectRestarts=0, registryMutationsOnSelection=0, registryVersionUpdatesOnSelection=0.
• node --test scripts/test-list-registry-stable-order.mjs
• pnpm test (passes; live Electron crash recovery test skipped because Electron is not launchable here)
• pnpm check:i18n (exits 0; reports existing Italian missing keys: settings.ai.whisper.vocabulary, settings.extensions.appSearchScope)
• pnpm build:main
• pnpm build:renderer
• LSP diagnostics for src/renderer/src/raycast-api/list-runtime-renderers.tsx: no errors
• Optional pnpm exec tsc -p tsconfig.renderer.json --noEmit still fails on existing renderer-wide type debt outside this change.

[JustYannicc]

Superseded by the consolidated renderer performance PR #533: #533. Closing this scoped source PR so review stays centralized there.