feat(gui): cozy library redesign (v0.3.0)

[GregTheGreek]

Summary

Reworks the Rompatch GUI from a single-flow patcher into a small library + patcher app per the design handoff in ~/Desktop/romdesign/. The aim is a warm, library-like experience for non-technical players, while keeping all the existing verify / re-apply / export plumbing reachable.

What's new

• Design tokens: warm light + dark themes (oklch), four user-selectable accents, Instrument Serif italic display / Geist UI / JetBrains Mono pairing.
• Sidebar: cartridge brand mark, Library / Patcher / Discover hacks nav, Preferences footer.
• Library: page header, search, segmented filter (All / Base / Patched), grid + list layouts. Base ROMs and Patched ROMs render in separate sections — patched ROMs are first-class cards with a format badge and a based on <BaseTitle> subline. Search matches against patch names too.
• ROM detail slide-over (RomDetail.tsx): 520 px right-side panel with two modes (base / patched) navigated via a based on… pill. Download flow re-verifies the recorded hash before exporting and refuses on mismatch. Remove confirm copy adapts: base-with-N-patches / base-alone / patched.
• Preferences modal (PreferencesModal.tsx): four sections — Appearance (Theme + Accent), Patching (strip header + fix checksum, persisted to localStorage and used to seed the patcher's Advanced defaults), Storage (library folder picker via librarySetRoot), About.
• Patcher save strip: filename on top with double-click to rename, directory + "Change folder" beneath. Library refreshes immediately after a successful apply so the new patched ROM lands in the library without a manual refresh.

Backend

• New library_reveal_rom(rom_hash) IPC so the slide-over can reveal a base ROM even when no patches reference it yet. Wraps the existing rom_path_for + reveal_in_finder.

Test plan

• pnpm typecheck + cargo check -p rompatch-gui both pass.
• Import a base ROM via the Library "Add ROM" button and via drag-drop; card appears in the Base section.
• Apply a patch in the Patcher; new card appears in the Patched section without reload, sidebar count updates.
• Click a base card → slide-over opens in base mode; click a patched card → slide-over opens directly in patched mode; click the based on… pill → navigates back to the base view within the same overlay.
• Patched-mode Download: untouched patched output exports cleanly; corrupt the patched output file on disk between apply and download → download is refused with a danger toast.
• Remove confirm copy adapts to base-with-N / base-alone / patched.
• Reveal-in-Finder works from both header buttons.
• Preferences → Patching: toggles persist across reload and seed the patcher's Advanced section on next visit.
• Preferences → Storage: choose a new library folder, library reloads from the new location.
• Preferences → Appearance: theme + accent persist; the pre-paint resolver in index.html matches on next launch.