Add Active Save File search

[woahitsraj]

Summary

• Add a compact command-style Search for the Active Save File by species, nickname, or location.
• Open Search with Cmd/Ctrl+K or controller Y; open the Main Menu with Cmd/Ctrl+Shift+K or controller Start.
• Open the exact Party or Box Slot from a result and restore keyboard or controller focus.
• Render global shortcuts in Settings from the same typed app-command registry used by input handling, including a readable narrow-screen layout.
• Keep search local and offline, with clear empty and unavailable Save File states.

Verification

• pnpm lint
• pnpm typecheck
• pnpm test:unit -- --run, 456 passed
• pnpm test:engine-smoke, 144 passed
• pnpm exec playwright test src/routes/quick-search.e2e.ts src/routes/main-menu.e2e.ts src/routes/settings.e2e.ts, 23 passed
• Focus and transition regression scenarios, 10 passed across 5 repetitions each
• Full CI browser matrix, 131 passed
• dotnet build engine/Pksx.Pkhex.Engine/Pksx.Pkhex.Engine.csproj
• dotnet format engine/Pksx.Pkhex.Engine/Pksx.Pkhex.Engine.csproj --verify-no-changes
• Svelte autofixer, no issues or suggestions
• Desktop and 390px-wide browser verification

Closes #254

[github-actions]

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Staging	staging.pksx.app

Updated for commit 58bfe41. View workflow run.