Merge origin/master: session projection base, command channel, composer seats

Resolution follows the reattachment plan: the #587 wire layer (planMode/
setPlanMode RPC, prompt.planMode, client Session projection fences) is
dropped in favor of the session-projection base now on master; master
structure wins in all shared files. Kept from the PR side: the approval-only
pending filter in ChatView (questions render solely through the composer
takeover) and the auto-merged QuestionComposer improvements. The deleted
host/runtime package and retired test carriers are removed with master.

packages/client/ui-question/src/client/QuestionComposer.module.css

@@ -19,6 +19,13 @@
   background: var(--dsw-specific-input-major);
   box-shadow: var(--dsw-shadow-lv1-blur);
   color: var(--dsw-alias-label-primary);
+  /* Elevated surface in dark, same as the menus: the option list inside scrolls
+     once the card hits the cap above, so the thumb takes the l2 pair. Declared
+     on the card because the elevation belongs to the surface, and the custom
+     properties inherit down to `.options` (see ui-theme styles/scrollbar.css
+     for the rebinding contract). */
+  --dsh-scrollbar-thumb: var(--dsw-alias-scrollbar-bg-l2);
+  --dsh-scrollbar-thumb-hover: var(--dsw-alias-scrollbar-hover-l2);
 }
 
 .card,
@@ -130,6 +137,11 @@
   gap: 10px;
   width: 100%;
   min-height: 42px;
+  /* Rows are the scroll content, never the slack absorber: a shrinkable row
+     collapses to min-height while its wrapped copy keeps the taller
+     intrinsic height, and centered content then paints outside the row box —
+     over the title and the next row. Overflow belongs to .options. */
+  flex-shrink: 0;
   padding: 5px 8px;
   border: 1px solid transparent;
   border-radius: 12px;
@@ -210,6 +222,9 @@
 }
 
 .custom {
+  /* Same reason as .option: the custom block is scroll content, and shrinking
+     it pushes its trigger row (and the open textarea) past the footer. */
+  flex-shrink: 0;
   border: 1px solid transparent;
   border-radius: 12px;
 }

packages/client/ui-question/src/client/QuestionComposer.tsx

@@ -37,6 +37,8 @@ export function parseQuestionTitle(title: string): string {
 
 /** Return whether a textarea key event belongs to an active IME composition. */
 function isComposing(event: KeyboardEvent<HTMLTextAreaElement>): boolean {
+  // keyCode 229 is the legacy IME-composition signal engines emit without isComposing.
+  // eslint-disable-next-line @typescript-eslint/no-deprecated
   return event.nativeEvent.isComposing || event.nativeEvent.keyCode === 229
 }
 
@@ -61,7 +63,10 @@ function QuestionFlow({ pending }: { pending: PendingQuestion }) {
   })))
   const [busy, setBusy] = useState<'answer' | 'cancel' | null>(null)
   const [error, setError] = useState<string | null>(null)
+  // index stays in bounds (every setIndex site clamps) and drafts mirrors questions 1:1.
+  // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
   const question = questions[index]!
+  // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
   const draft = drafts[index]!
   const hasOptions = (question.options?.length ?? 0) > 0
 
@@ -145,10 +150,10 @@ function QuestionFlow({ pending }: { pending: PendingQuestion }) {
   const skipQuestion = (): void => {
     const nextDrafts = drafts.map((item, itemIndex) => itemIndex === index
       ? {
-          selected: [], custom: '',
-          customOpen: (question.options?.length ?? 0) === 0,
-          skipped: true,
-        }
+        selected: [], custom: '',
+        customOpen: (question.options?.length ?? 0) === 0,
+        skipped: true,
+      }
       : item)
     setDrafts(nextDrafts)
     setError(null)