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.

CHANGELOG.md

@@ -62,11 +62,14 @@ and adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
   This also takes about 3 MB of grammar files and two dependencies out of the install.
 
+- **The viewer's screens are now a component library other tools can render.** The Symbol view, the Flow strip and the Map are packaged as `@colbymchenry/codegraph-ui` — the same components `codegraph ui` draws, not a copy of them — so another application can show you a symbol's callers, a call path or your architecture over its own copy of the graph. Everything a screen knows arrives through one small interface it is handed, so the tool doing the rendering decides where the data comes from and where a click goes; a design-token stylesheet ships with it so the screens can be themed to match whatever they are embedded in. It is versioned with the engine, so the reader and the graph it reads always match.
+
+  Nothing changes for `codegraph ui` itself — it is the same viewer, now the library's first user. The package is prepared, not yet on npm.
+
 ### Fixes
 
 - Fixed a long-running `codegraph ui` session serving a symbol that a sync had already deleted. The viewer keeps one connection to your index open, and its in-memory lookup didn't notice when another process — your agent's sync, or `codegraph sync` — rewrote the file underneath it, so a symbol screen could keep showing a body with no callers while search correctly reported it had moved. Because a symbol's identity includes the line it starts on, this happened after almost any edit above it.
 
-
 ## [1.6.0] - 2026-08-26
 
 ### Highlights