Migrate to GTKX 1.6, fix unit conversion, add home-use limits

[tduarte]

Why

pnpm install no longer works on main. The pinned @gtkx/react@0.11.1 depends on @gtkx/ffi, and every version of that package has been removed from npm. GTKX is now at 1.6, where @gtkx/ffi became @gtkx/runtime, and the API changed enough that this is a port rather than a version bump.

What changed

App (src/app.tsx, src/utils/calculations.ts)

• Ported to the GTKX 1.6 API. Bindings are generated per project (@gtkx/gi/*, @gtkx/jsx/*) by gtkx codegen.
• Preferences and About now use AdwPreferencesDialog and AdwAboutDialog instead of separate portaled windows.
• The header bar menu is a GMenu driven by win.preferences/win.about actions. Ctrl+, is registered as an app accelerator.
• The brew method is a ComboRow that shows the ratio as its subtitle. Coffee and water are AdwSpinRows.
• Unit conversion fix: coffee weight in grams is now the only stored value, and everything on screen is derived from it. Switching units converts the amounts (30 g ↔ 1.06 oz) without drift. Before, the raw number was kept, so 20 g became 20 oz.
• Home-use limits: each method has a maximum water volume (MAX_WATER_ML). The coffee maximum is derived from it through the ratio, so the two rows never clamp out of sync:
  • Espresso: 60 ml / 30 g
  • Pour Over: 1200 ml / 80 g
  • French Press: 1500 ml / 125 g
  • AeroPress: 500 ml / 45 g
• Changing method clamps the coffee to the new limit. The water +/- step is now 5 ml (0.25 fl oz).
• Removed leftover debug fetch() calls that posted app state to 127.0.0.1:7242.

Tooling and packaging

• gtkx.config.ts replaces the app ID in package.json. The scripts are now pnpm dev, typecheck, build and build:flatpak.
• gtkx deploy --target flatpak generates the manifest, desktop entry and metainfo, and bundles Node. This replaces:
  • the hand-written flatpak/ manifest and its @gtkx/native wrapper
  • the SEA scripts, scripts/bundle.ts, src/dev.tsx and tsconfig.app.json
• The runtime is now GNOME 50, because GTKX 1.x needs GTK 4.20 and Adwaita 1.8. Icons moved to data/icons/ in the hicolor layout.
• vite.config.ts excludes build/ from the dev watcher. The Flatpak build tree contains symlink loops that ran gtkx dev out of memory.
• CI now uses Node 24, runs the typecheck, and builds with pnpm build:flatpak in the gnome-50 container.
• Fixed stale monorepo paths in run-dev.sh and the README. tsconfig.app.tsbuildinfo is no longer tracked.
• Added CLAUDE.md. AGENTS.md is generated by gtkx codegen, which recommends committing it.

Flatpak releases (added later in this PR)

Ported the release flow from tduarte/Scribe. Pushing a v* tag that matches package.json's version runs .github/workflows/release.yml, which:

1. builds the tag with gtkx deploy;
2. GPG-signs the OSTree repo with build-aux/publish-repo.sh;
3. publishes the repo to GitHub Pages, along with a .flatpakref, a .flatpakrepo and a landing page;
4. attaches the .flatpak bundle to the GitHub release.

Tested locally with a throwaway key. Installing from the served .flatpakref into a scratch FLATPAK_USER_DIR worked, with gpg-verify=true and gpg-verify-summary=true, and flatpak update and remote-ls worked against it. One-time setup is still needed before the first tag (see docs/RELEASING.md):

• add the FLATPAK_GPG_PRIVATE_KEY secret;
• enable Pages with GitHub Actions as the source;
• add a v* tag rule to the github-pages environment.

The CI workflow also got a fix: SWC's native addon refused the container's world-writable HOME as its cache root, so caches now go under /root/.cache.

Testing

• pnpm typecheck and pnpm build pass.
• pnpm build:flatpak built build/out/io.github.tduarte.cafe-1.0.0-x86_64.flatpak (26 MiB) locally. The bundle has not been installed or run.
• I drove the running app through the GTKX MCP server:
  • Calculation works in both directions.
  • The menu opens both dialogs, which also close correctly.
  • Pour Over limits hold at both ends (0 and 80 g ↔ 1200 ml).
  • Switching to French Press or Espresso keeps or clamps the coffee correctly.
  • Metric → Imperial → Metric comes back exactly (30.0 g / 60 ml).

Reviewer notes

• CI is unverified. The new workflow has only been written, not run. Watch the first run on this PR.
• Changing units or method rebuilds the spin rows (key). This is deliberate: otherwise GTK can apply the new value before the new bounds, clamp it, and report it back as a user edit. The comments in app.tsx and CLAUDE.md explain it.

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