feat(ui): add browser console served by the daemon

Introduce a minimal operations console reachable on a dedicated UI port
(default 8081), kept separate from the OpenAI-compatible API port.

- ts_web/ holds the SPA shell (index.html, app.css, vanilla app.js) with
  sidebar navigation for all views from readme.ui.md and a working
  Overview page backed by a new /_ui/overview JSON endpoint.
- scripts/bundle-ui.ts walks ts_web/ and emits ts_bundled/bundle.ts, a
  single generated module exporting every asset as base64. Mirrors the
  @stack.gallery/registry pattern so deno compile binaries embed the
  entire UI with no external filesystem dependency at runtime.
- ts/ui/server.ts (UiServer) serves assets from either the bundled map
  (default, prod) or directly from ts_web/ on disk (dev). The source is
  chosen per-config and can be overridden by UI_ASSET_SOURCE=disk|bundle.
  SPA fallback routes unknown extensionless paths to index.html.
- IModelGridConfig.ui block with enabled/port/host/assetSource defaults;
  config init writes the block, the normalizer fills in defaults on
  load, and the daemon starts/stops the UI server alongside the API.
- deno.json gains a bundle:ui task; compile:all now depends on it so
  released binaries always contain an up-to-date bundle. dev task sets
  UI_ASSET_SOURCE=disk for hot edits.
- ts_bundled/ is gitignored (generated on build).
- test/ui-server.smoke.ts exercises bundle and disk modes end to end
  (index, app.js, SPA fallback, /_ui/overview, 404).

ts/modelgrid.ts

@@ -316,6 +316,12 @@ export class ModelGrid {
         cors: config.api?.cors ?? true,
         corsOrigins: config.api?.corsOrigins || ['*'],
       },
+      ui: {
+        enabled: config.ui?.enabled ?? true,
+        port: config.ui?.port || 8081,
+        host: config.ui?.host || '0.0.0.0',
+        assetSource: config.ui?.assetSource === 'disk' ? 'disk' : 'bundle',
+      },
       docker: {
         networkName: config.docker?.networkName || 'modelgrid',
         runtime: config.docker?.runtime || 'docker',