[raiseCatError]

Stacked on #517 (Ghostty native shaders), so this diff is Slice 4 only. Retarget only after review.

What

• /appearance › Effects routing: a read-only view of who draws each animated surface now (host GPU shader, NMSh's Portable renderer, or nothing) and why.
  • It reads the one cursor backend choice, the presentation gates, Settings › Motion, and NMSh's written host passes. It never schedules or draws anything; Transitions and chooseBackend stay the only decision makers.
  • Only the cursor and whole-window focus/display passes are ever routed to the host. Prompt transitions, command feedback, notifications, the screensaver and the welcome are always Portable or off: a terminal shader sees the whole window, not NMSh's rows.
  • Host-specific reads live in src/appearance/nativePasses.ts. TerminalApp stays host-neutral, and the guard test passes.
• Chroma-driven Aurora (Ghostty): Colors = Follow Chroma (default) or Custom.
  • Follow Chroma uses the idle visuals' Follow Chroma / Theme resolver.
  • NMSh's passes are re-synced on Chroma or theme settings changes, never per event. Ghostty applies them on its next reload.
  • Aurora settings saved earlier with their own colors keep them.

Verification

• Focused tests for the changed modules and their consumers: 162/162. Typecheck clean.
• Independent review found no blocker. Its 5 should-fix items were fixed with regression tests.
• The full suite is left to CI: the local machine was under heavy external load, and only tests related to this work were run locally.

Not verified: physical Ghostty/Kitty QA and GPU rendering were not run.