fix(ui-trajectory): own composer overlay geometry

packages/client/ui-conversation/src/client/skeleton/ConversationRoot.module.css

@@ -208,6 +208,26 @@
   );
 }
 
+/* Views may opt into a composer overlay while ConversationRoot retains
+   ownership of the seat geometry and its active-phase precedence. */
+.scrollBody:has([data-conversation-composer-overlay]) {
+  position: relative;
+  overflow: hidden;
+}
+
+.scrollBody:has([data-conversation-composer-overlay]) > .viewArea {
+  flex: 1 1 0;
+  min-height: 0;
+  overflow: hidden;
+}
+
+.scrollBody:has([data-conversation-composer-overlay]) > .composerSeat {
+  position: absolute;
+  right: 0;
+  bottom: 0;
+  left: 0;
+}
+
 /* Hero phase: the composer stack (hero chrome + workspace row + card) is
    flex-centered in the column; composer phase docks it at the bottom. Flex,
    NOT absolute+transform: a transform would make this box the containing

packages/client/ui-trajectory/src/client/TrajectoryTable.module.css

@@ -15,7 +15,8 @@
 .tablePane {
   flex: 1;
   min-width: 0;
-  overflow: auto;
+  overflow-x: hidden;
+  overflow-y: auto;
   padding-bottom: var(--dsh-trajectory-bottom-clearance, 0px);
   container: trajectory-table / inline-size;
 }
@@ -28,7 +29,7 @@
   );
 
   width: 100%;
-  min-width: 480px;
+  min-width: 0;
   border-spacing: 0;
   table-layout: fixed;
   color: var(--dsw-alias-label-primary);
@@ -905,7 +906,8 @@
 .detailBody {
   flex: 1;
   min-height: 0;
-  overflow: auto;
+  overflow-x: hidden;
+  overflow-y: auto;
   padding-bottom: var(--dsh-trajectory-bottom-clearance, 0px);
   scrollbar-gutter: stable;
 }

packages/client/ui-trajectory/src/client/TrajectoryView.tsx

@@ -459,7 +459,7 @@ export function TrajectoryView({
   }
 
   return (
-    <div className={css.root}>
+    <div className={css.root} data-conversation-composer-overlay="">
       <TrajectoryToolbar
         actualDuration={actualDuration}
         onActualDurationChange={(nextActualDuration) => {

packages/client/ui-trajectory/src/client/views.module.css

@@ -13,30 +13,6 @@
   background: var(--dsw-alias-bg-layer-1);
 }
 
-/* Trajectory keeps the ledger and details panel inside the remaining
- * conversation height; only the internal panes scroll. The composer floats
- * over the ledger like chat's sticky seat — absolute, not sticky, because
- * this host does not scroll. */
-:global([data-conversation-scroll]):has(.root) {
-  position: relative;
-  overflow: hidden;
-}
-
-:global([data-conversation-scroll]):has(.root) > :first-child {
-  flex: 1 1 0;
-  min-height: 0;
-  overflow: hidden;
-}
-
-/* div qualifier outranks ConversationRoot's active-phase sticky rule (equal
- * specificity otherwise, and cross-module source order is bundler-defined). */
-:global([data-conversation-scroll]):has(.root) > :global(div[data-composer-seat]) {
-  position: absolute;
-  right: 0;
-  bottom: 0;
-  left: 0;
-}
-
 .ledger {
   position: relative;
   z-index: 0;
@@ -47,8 +23,6 @@
   min-width: 0;
   overflow: hidden;
 
-  /* Internal panes reserve the floating composer's live height plus a 16px
-   * breathing gap so end rows and detail bodies can scroll clear of the
-   * overlay. */
+  /* ConversationRoot publishes the floating composer's live height. */
   --dsh-trajectory-bottom-clearance: calc(var(--dsh-composer-height, 152px) + 16px);
 }

packages/client/ui-trajectory/tests/views.spec.tsx

@@ -288,6 +288,7 @@ describe('tab switching in ConversationRoot', () => {
     expect(screen.queryByRole('columnheader')).toBeNull()
     expect(screen.getByRole('toolbar', { name: 'Trajectory toolbar' })).toBeTruthy()
     expect(screen.getByRole('region', { name: 'Trajectory timeline' })).toBeTruthy()
+    expect(view.container.querySelector('[data-conversation-composer-overlay]')).toBeTruthy()
     fireEvent.click(screen.getByRole('button', { name: 'Collapse turns' }))
     expect(view.container.querySelector('[data-collapsed-summary="turn"]')).toBeTruthy()
     fireEvent.click(screen.getByRole('button', { name: 'Expand turns' }))