Task #514: Align note composer with folders rail

Original task: On the Notes page the "اكتب ملاحظة" composer sat alone
in a full-width row above the content row, while the "المجلدات"
FoldersRail started in the row below. Composer appeared high, rail
visibly lower with empty space between them.

Change:
- Moved the top composer out of its standalone full-width block and
  into the left content column (`flex-1 min-w-0`) of the existing
  folders+content row in `artifacts/tx-os/src/pages/notes.tsx`. Both
  now share the same row, so the composer's top edge aligns with the
  rail's top edge on desktop.
- Added a `className?: string` prop to `FoldersRail`
  (`artifacts/tx-os/src/components/notes/folders-rail.tsx`) appended
  to its root <aside>, so the page can pass `order-*` classes.
- On narrow widths (`flex-col`) the composer column gets
  `order-1 md:order-2` and the rail gets `order-2 md:order-1` ONLY
  when `showTopComposer` is true. In hidden-composer views (Inbox /
  Sent / Archived / Shared-with-me) no order classes are applied, so
  the rail/content stacking order on mobile stays exactly as it was
  before this task. Result: composer stacks ABOVE the rail on mobile
  in My Notes (preserving the original mobile reading order) and
  sits beside it on md+, with zero behavior change in the other
  views.

Behavior preserved:
- `showTopComposer` gating unchanged — still hidden on Inbox / Sent /
  Archived / Shared-with-me.
- `data-testid="notes-top-composer"` preserved.
- FoldersRail's existing width/scroll classes unchanged; new className
  is purely additive.
- Stale comment about composer being "above the folders area" updated
  to describe the new in-column placement and the order-* mobile
  behavior.

Verification: `pnpm --filter @workspace/tx-os exec tsc --noEmit`
passes. No test files reference the composer block by structural
selectors that the move would break.

No deviations from the plan.

artifacts/tx-os/src/pages/notes.tsx

@@ -794,10 +794,10 @@ export default function NotesPage() {
             totalCount={notes.length}
             onShareFolder={(f) => setFolderShareFor(f)}
             mode={view === "active" && folderSelection.kind === "all" ? "chips-only" : "rail"}
-            className="order-2 md:order-1"
+            className={showTopComposer ? "order-2 md:order-1" : undefined}
           />
         )}
-        <div className="flex-1 min-w-0 order-1 md:order-2">
+        <div className={`flex-1 min-w-0${showTopComposer ? " order-1 md:order-2" : ""}`}>
         {showTopComposer && (
           <div className="mb-4" data-testid="notes-top-composer">
             <Composer