fix(task-editor): prevent preview pane and work log from flex-shrinking

.task-main is a flex column. Children default to flex-shrink: 1, so
when body content is taller than the available column height, flex
squeezes .preview-pane back to its min-height (200px) and the
overflow renders visibly on top of subsequent siblings — making the
TaskLogSection appear in the middle of the body content.

Surfaced by viewing a task with an unusually long markdown body in
preview mode. Pre-existed PR 1, just rarely hit.

NoteEditorView uses the standard block-flow .editor-main and isn't
affected.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/views/TaskEditorView.vue

@@ -737,12 +737,19 @@ useEditorGuards(dirty, save);
   border-bottom: 1px solid var(--color-border);
 }
 
+/* .task-main is a flex column; without flex-shrink: 0, long body content
+   gets squeezed back to min-height and overflows visibly on top of siblings. */
+.body-editor-wrap,
+.body-log {
+  flex-shrink: 0;
+}
+
 .body-editor-wrap {
   min-height: 200px;
 }
 
-.body-log {
-  /* TaskLogSection already has its own border/bg */
+:deep(.preview-pane) {
+  flex-shrink: 0;
 }
 
 /* Right sidebar: metadata fields */