style(app-mode): flush left-dock + surface Run errors as toast

- Move output history thumbs from column 1 to row 1 so column 1 is
  free for the left-dock panel to sit flush against the SideToolbar.
- Drop the column-1 clearance from .floating-panel--left-dock /
  --float-tl / --float-bl left offsets (and matching drag-preview
  positions); left edge now mirrors right-dock at the outer padding.
- RunCell: route queue-prompt failures through toastErrorHandler
  instead of console.error so silent failures surface to the user.

src/components/appMode/layout/LayoutView.vue

@@ -461,32 +461,27 @@ const cells = computed<LayoutCellPlacement[]>(() => {
   // Action cells on row 1, right of builder/share. Only mount when
   // a history item is selected (mirrors LinearPreview's top bar).
   if (hasSelection.value) {
-    const actionStartCol = col
-    out.push({
-      id: 'action-rerun',
-      col: actionStartCol,
-      row: 1,
-      kind: 'action-rerun'
-    })
+    out.push({ id: 'action-rerun', col: col++, row: 1, kind: 'action-rerun' })
     out.push({
       id: 'action-reuse-params',
-      col: actionStartCol + 1,
+      col: col++,
       row: 1,
       kind: 'action-reuse-params'
     })
     out.push({
       id: 'action-download',
-      col: actionStartCol + 2,
+      col: col++,
       row: 1,
       kind: 'action-download'
     })
     out.push({
       id: 'action-info',
-      col: actionStartCol + 3,
+      col,
       row: 1,
       colSpan: 3,
       kind: 'action-info'
     })
+    col += 3
   }
 
   out.push({
@@ -497,13 +492,13 @@ const cells = computed<LayoutCellPlacement[]>(() => {
     kind: 'system-feedback'
   })
 
-  // History thumbs stack down column 1 starting below the chrome row.
-  const thumbStartRow = 2
+  // History thumbs sit on row 1, right of the action cells. Keeps column 1
+  // clear so the left-dock panel snaps flush against the SideToolbar.
   for (let i = 0; i < historyThumbs.value.length; i++) {
     out.push({
       id: historyThumbs.value[i].id,
-      col: 1,
-      row: thumbStartRow + i,
+      col: col + i,
+      row: 1,
       kind: 'output-thumb'
     })
   }

src/components/appMode/layout/cells/RunCell.vue

@@ -7,10 +7,12 @@
  */
 import { useI18n } from 'vue-i18n'
 
+import { useErrorHandling } from '@/composables/useErrorHandling'
 import { useCommandStore } from '@/stores/commandStore'
 
 const { t } = useI18n()
 const commandStore = useCommandStore()
+const { toastErrorHandler } = useErrorHandling()
 
 async function handleClick(e: Event) {
   const priority = 'shiftKey' in e && (e as KeyboardEvent | MouseEvent).shiftKey
@@ -23,9 +25,7 @@ async function handleClick(e: Event) {
       }
     })
   } catch (error) {
-    // Surface failures in the console so we can diagnose instead of
-    // the button silently doing nothing.
-    console.error('[RunCell] Queue prompt failed:', error)
+    toastErrorHandler(error)
   }
 }
 </script>

src/components/appMode/layout/panels/FloatingPanel.vue

@@ -81,19 +81,15 @@ const positionClass = computed(() => [
   right: var(--layout-outer-padding);
   bottom: var(--layout-outer-padding);
 }
-/* Left-side presets: left edge clears col 1 (icons), top edge clears
-   row 1 (mode toggle + action cells). This places the panel's
-   top-left corner snug at the intersection of the icon column and
-   the mode-toggle row. */
+/* Left-side presets: top edge clears row 1 (mode toggle + action cells);
+   left edge sits flush at the outer padding (mirroring right-dock) so
+   the panel docks snug against the SideToolbar. */
 .floating-panel--left-dock {
   top: calc(
     var(--layout-outer-padding) + var(--layout-cell-size) +
       var(--layout-gutter-min)
   );
-  left: calc(
-    var(--layout-outer-padding) + var(--layout-cell-size) +
-      var(--layout-gutter-min)
-  );
+  left: var(--layout-outer-padding);
   bottom: calc(
     var(--layout-outer-padding) + var(--layout-cell-size) +
       var(--layout-gutter-min)
@@ -114,21 +110,15 @@ const positionClass = computed(() => [
     var(--layout-outer-padding) + var(--layout-cell-size) +
       var(--layout-gutter-min)
   );
-  left: calc(
-    var(--layout-outer-padding) + var(--layout-cell-size) +
-      var(--layout-gutter-min)
-  );
+  left: var(--layout-outer-padding);
   height: calc(50% - var(--layout-outer-padding) - 4px);
 }
 .floating-panel--float-bl {
   bottom: calc(
     var(--layout-outer-padding) + var(--layout-cell-size) +
       var(--layout-gutter-min)
   );
-  left: calc(
-    var(--layout-outer-padding) + var(--layout-cell-size) +
-      var(--layout-gutter-min)
-  );
+  left: var(--layout-outer-padding);
   height: calc(50% - var(--layout-outer-padding) - 4px);
 }
 

src/components/appMode/layout/panels/PanelDragPreview.vue

@@ -54,10 +54,7 @@ const presetClass = computed(() => `panel-drag-preview--${props.preset}`)
     var(--layout-outer-padding) + var(--layout-cell-size) +
       var(--layout-gutter-min)
   );
-  left: calc(
-    var(--layout-outer-padding) + var(--layout-cell-size) +
-      var(--layout-gutter-min)
-  );
+  left: var(--layout-outer-padding);
   bottom: calc(
     var(--layout-outer-padding) + var(--layout-cell-size) +
       var(--layout-gutter-min)
@@ -78,21 +75,15 @@ const presetClass = computed(() => `panel-drag-preview--${props.preset}`)
     var(--layout-outer-padding) + var(--layout-cell-size) +
       var(--layout-gutter-min)
   );
-  left: calc(
-    var(--layout-outer-padding) + var(--layout-cell-size) +
-      var(--layout-gutter-min)
-  );
+  left: var(--layout-outer-padding);
   height: calc(50% - var(--layout-outer-padding) - 4px);
 }
 .panel-drag-preview--float-bl {
   bottom: calc(
     var(--layout-outer-padding) + var(--layout-cell-size) +
       var(--layout-gutter-min)
   );
-  left: calc(
-    var(--layout-outer-padding) + var(--layout-cell-size) +
-      var(--layout-gutter-min)
-  );
+  left: var(--layout-outer-padding);
   height: calc(50% - var(--layout-outer-padding) - 4px);
 }
 </style>