feat(ui): the viewer's screens as @colbymchenry/codegraph-ui, behind one adapter (CG-61)

`ui/src` now builds two ways from one tree: the static app `codegraph ui`
serves, and — via `svelte-package` — a Svelte library the Pro app imports.
A forked component would be a second answer to the same question about the
same graph, so there is no fork.

Everything a screen knows arrives through a `GraphAdapter`: eleven methods
answering the wire shapes verbatim, with `createHttpAdapter()` (the loopback
JSON API) as the default and a host's in-process engine reads as the point.
`lib/api.ts` became a one-line-per-call facade over it, which is why no call
site in the views changed. The payload types moved to `lib/wire.ts` — no
imports, no runtime — so a host can depend on the vocabulary alone.

Two more seams and one guard:

- `lib/navigation.ts` holds the href builders behind a `NavigationDriver`, so
  a host addresses its own URL space. The app's half — the hash parser and the
  live route, which attach window listeners at module scope — stays in
  `router.svelte.ts` and is pruned out of the package: rendering a Symbol view
  must not install a hash router in somebody else's application.
- `lib/theme.css` carries the design tokens and maps Svelte Flow's `--xy-*`
  variables onto them, so a host never sees library defaults. Dark now also
  answers to a bare `[data-theme]`, which is how `<CodegraphUi theme>` themes
  a container rather than the document.
- `scripts/check-ui-package.mjs` prunes the app's shell, resolves the
  extensionless specifiers svelte-package leaves behind, and asserts that
  nothing but `lib/adapter.js` reaches the network.

The search box, its keyboard and its panel are one component now
(`SearchPalette`), because splitting them is what breaks a palette.

`__tests__/ui-package.test.ts` mounts the three screens from the package entry
against a mock adapter in jsdom; it runs as a second vitest project so the
`browser` resolve condition it needs cannot reach the engine's suites.

Versioned with the engine. Prepared, not published: `private: true` is the
guard and `pack-npm.sh` only packs a tarball under CODEGRAPH_PACK_UI=1.

ui/src/app.css

@@ -1,107 +1,16 @@
 /* =====================================================================
-   codegraph ui — design tokens + global primitives
+   codegraph ui — the app's global primitives
 
-   The engine's paper/ink editorial system (site/src/styles/theme.css),
-   as specified in docs/design/codegraph-ui-design-spec.md §2: flat,
-   hairline rules, square corners everywhere, no shadows, no gradients,
-   sentence case, one oxblood accent, one amber (the "untested" badge).
+   The design tokens themselves live in `lib/theme.css`, which is also
+   what `@colbymchenry/codegraph-ui` exports for a host to import and
+   override. This file is everything ON TOP of them that only the
+   standalone viewer needs: the reset, the shell grid, and the handful of
+   primitives shared across views.
 
    Component-specific rules live in each .svelte file's scoped <style>.
-   Only tokens, resets and cross-view primitives belong here.
    ===================================================================== */
 
-/* ---------- tokens: light / paper (the bare :root set) ---------- */
-:root {
-  --paper: #f7f6f2;
-  --paper-2: #f1efe8;
-  --press: #e8e6dd;
-  --press-2: #dedbd0;
-  --ink: #16150f;
-  --ink-2: #56544a;
-  --ink-3: #87847a;
-  --ink-4: #b4b1a5;
-  --rule: #16150f;
-  --rule-soft: #d6d3c8;
-  --rule-faint: #e6e3d9;
-  --accent: #7a2230;
-  --accent-ink: #5e1a25;
-  --accent-soft: #f0e3e5;
-  --accent-line: #d9b3b9;
-  --amber: #8a5a0b;
-  --amber-soft: #f3e9d2;
-
-  /* The one code colour that is not a plain re-use of the ink ramp.
-     The spec asks for comments at --ink-3; measured against --paper that
-     is 3.46:1 and against the hot-line tint --accent-soft it is 3.00:1,
-     both under the 4.5:1 an AA reading of 12.5px body text needs. This is
-     the smallest step DOWN the same warm-grey ramp that clears 4.5:1 on
-     all three backgrounds a code line can have (paper 5.23, paper-2 4.92,
-     accent-soft 4.53) while staying quieter than --ink-2, which strings
-     and numbers use — so the recession order the spec describes is
-     unchanged, only legible. Dark needed the mirror step UP (4.51 on
-     accent-soft, where --ink-3 was 4.10). */
-  --code-comment: #6a675d;
-
-  --sans: 'Archivo Variable', 'Archivo', -apple-system, BlinkMacSystemFont, 'Helvetica Neue', Arial, sans-serif;
-  --mono: 'IBM Plex Mono', ui-monospace, 'SF Mono', Menlo, Consolas, monospace;
-  --code-size: 12.5px;
-  --code-lh: 20px;
-
-  /* App-shell geometry, shared by the grid and by anything that has to
-     offset itself under the bars (sticky rail headers, SVG overlays). */
-  --topbar-h: 48px;
-  --trailbar-h: 34px;
-
-  color-scheme: light dark;
-}
-
-/* ---------- tokens: dark / ink ----------
-   Every colour is defined on the bare :root above; these blocks only
-   redefine. `:not([data-theme="light"])` lets an explicit light choice
-   win over the OS preference. */
-@media (prefers-color-scheme: dark) {
-  :root:not([data-theme='light']) {
-    --paper: #16150f;
-    --paper-2: #1c1a14;
-    --press: #23211a;
-    --press-2: #2c2a22;
-    --ink: #f3f1ea;
-    --ink-2: #b8b5a8;
-    --ink-3: #87847a;
-    --ink-4: #5d5b52;
-    --rule: #f3f1ea;
-    --rule-soft: #34322a;
-    --rule-faint: #26241d;
-    --accent: #d48b96;
-    --accent-ink: #e5a5ae;
-    --accent-soft: #33201f;
-    --accent-line: #6b3a42;
-    --amber: #d9a94a;
-    --amber-soft: #2e2716;
-    --code-comment: #8e8b81;
-  }
-}
-
-:root[data-theme='dark'] {
-  --paper: #16150f;
-  --paper-2: #1c1a14;
-  --press: #23211a;
-  --press-2: #2c2a22;
-  --ink: #f3f1ea;
-  --ink-2: #b8b5a8;
-  --ink-3: #87847a;
-  --ink-4: #5d5b52;
-  --rule: #f3f1ea;
-  --rule-soft: #34322a;
-  --rule-faint: #26241d;
-  --accent: #d48b96;
-  --accent-ink: #e5a5ae;
-  --accent-soft: #33201f;
-  --accent-line: #6b3a42;
-  --amber: #d9a94a;
-  --amber-soft: #2e2716;
-  --code-comment: #8e8b81;
-}
+@import './lib/theme.css';
 
 /* ---------- reset ---------- */
 html,