Merge the concurrent selector adaptation; ui-model stays the model owner

The remote side re-merged master (i18n workflow round) and restored the
pre-architecture ModelSelector package with the Session-side state
machine. Reconciliation keeps that merge's master content and reasserts
this branch's model architecture: business state lives in ui-model's
shared per-session directory (ctx.models), not on Session/
ConversationSnapshot; the input.model seat entry and the /model popup
stay the two same-source entries; the history modelTarget piggyback stays
removed. The ui-model-selector package, its roster row, and its allowlist
entry go; the smoke-real roster names ui-model.

apps/web/tests/smoke-real.e2e.ts

@@ -144,10 +144,14 @@ async function detailsTrack(page: Page): Promise<number> {
   return Number(cols.split(' ').pop()!.replace('px', ''))
 }
 
-// Readiness gate: `dsh web` serves ALL nine manifest plugins; until every UI
+// Readiness gate: `dsh web` serves all ten production manifest plugins; until every UI
 // plugin's client bundle exists and exports apply, the loader fail-louds and
 // the frame never appears.
-const UI_PLUGIN_DIRS = ['connection', 'runtime', 'ui-theme', 'locale', 'ui-layout', 'ui-sidebar', 'ui-settings', 'ui-settings-general', 'ui-models', 'ui-conversation', 'ui-question', 'ui-trajectory']
+const UI_PLUGIN_DIRS = [
+  'connection', 'runtime', 'ui-theme', 'locale', 'ui-layout', 'ui-sidebar',
+  'ui-settings', 'ui-settings-general', 'ui-models', 'ui-conversation',
+  'ui-model', 'ui-question', 'ui-trajectory',
+]
 const ROUND_DONE_MARKER = 'WEB_ROUND_DONE'
 const notReady = UI_PLUGIN_DIRS.filter((dir) => {
   const bundle = join(REPO_ROOT, 'packages/client', dir, 'lib/client.js')