fix(sidebar): synchronize collapsed rail motion

packages/client/ui-workspace/src/client/WorkspaceBrowser.module.css

@@ -240,11 +240,13 @@
 
 /* Rail variant (own .rail class from the wide owner prop — the region never
    reads the shell's class names): the two icon controls stack as 36x36
-   circles matching the shell's rail rhythm. */
+   circles matching the shell's rail rhythm. Both use the rail's shared base
+   left anchor so the outer shell can translate the whole region uniformly. */
 .rail .sectionHeader {
   gap: 0;
   padding-left: 0;
   margin-bottom: 12px;
+  justify-content: flex-start;
 }
 
 .rail .headerActions {

packages/client/ui-workspace/src/client/WorkspaceBrowser.tsx

@@ -3,11 +3,11 @@
  * `sidebar.workspaces` hole: section header (title + view options + add
  * workspace), search, the grouped tree or flat list, and the workspace
  * dialogs. Wide state renders the full browser; rail state renders the two
- * region icons (search / add workspace), each requesting shell expansion
- * through the owner share. Adding is the header button's one action, so it
- * raises the directory flow with no menu in between; the flow and its error
- * dialog live in WorkspacePicker (same package — direct composition, no slot
- * between them).
+ * region icons (search / add workspace) as 36px controls on the shell's shared
+ * rail entry path, each requesting expansion through the owner share. Adding is the header
+ * button's one action, so it raises the directory flow with no menu in
+ * between; the flow and its error dialog live in WorkspacePicker (same
+ * package — direct composition, no slot between them).
  */
 import { useEffect, useMemo, useRef, useState } from 'react'
 import clsx from 'clsx'