feat(terminal): replace ghostty-web with an in-repo libghostty-vt adapter

The terminal ran on the ghostty-web npm package plus a hand-written patch,
and every rendering bug (recycled rows, duplicated reflow fragments, prompt
artifacts) had to be worked around from outside. The emulator now is the
official libghostty-vt C ABI compiled to WebAssembly, driven by a browser
adapter ported from T3 Code (MIT, notice in LICENSE-T3CODE) and owned in
packages/ui/src/lib/ghostty. The artifact is reproducible with
scripts/build-libghostty-wasm.sh, including a workaround for Zig 0.15.2 on
macOS 27 SDKs.

On top of the port: one WASM instance per page with every tab kept mounted
and hidden tabs paused; history replayed at the PTY size it was drawn for;
shells spawned only after the first fitted grid so zsh never prints the
PROMPT_SP marker; box drawing, block elements and Powerline arrows drawn
procedurally to the exact cell so TUI borders and block logos have no gaps
between rows; a software-rasterized canvas so Gecko renders every tab's text
with the same smoothing; the symbols-only Nerd Font bundled instead of a CDN
fetch; touch selection and scrolling driven through the surface API; a copy
button in the tab strip for touch hosts; localized aria labels.

Testing: bun tests run the real WASM (reflow, palette, replay isolation,
recycled rows, box glyph geometry); viewport and view tests use a surface
double; verified in Chromium and Zen (windowed and headless) for crisp text,
new tabs, panel reopen, resize and box glyph rendering; package type-check,
oxlint/eslint on new files, web build.

packages/web/vite.config.ts

@@ -73,7 +73,7 @@ export default defineConfig({
       injectRegister: false,
       manifest: false,
       injectManifest: {
-        globPatterns: ['**/*.{js,css,html,ico,png,svg,woff,woff2,ttf,otf,eot}'],
+        globPatterns: ['**/*.{js,css,html,ico,png,svg,woff,woff2,ttf,otf,eot,wasm}'],
         // iOS Safari/PWA is much more reliable with a classic (non-module) SW bundle.
         rollupFormat: 'iife',
         // We already keep a custom manifest in index.html