Task #431: polish Send Note dialog (RTL X + search overlap)

Two visual issues in the "إرسال الملاحظة" dialog:

1. The shadcn DialogContent renders a built-in close (X) button hard
   pinned at `right-4 top-4`. In Arabic the dialog title is
   right-aligned and crashed into the X.
   Fix: add `pe-8` to the SendNoteDialog header so the title row
   reserves logical end-padding for the X in both directions. The
   shared dialog component is unchanged so other dialogs are untouched
   (out of scope per the task plan).

2. The recipient search field used inline `style={{ right|left: 10 }}`
   for the magnifier and a conditional `pe-9` / `ps-9` based on
   `i18n.language`. In RTL the icon collided with the placeholder.
   Fix: drop the conditional branching — position the icon with the
   logical class `start-2.5` and always pad the input with `ps-9`.
   The icon now sits at the inline-start edge in both LTR and RTL
   with a clear gutter to the placeholder/caret.

Skipped step 3 of the plan (i18n aria-label override on the X). It
required no locale changes and no rendering improvement, so per the
plan's own conditional ("only if step 3 keeps the override; otherwise
no locale changes") it was dropped to keep scope tight.

Verification:
- `pnpm exec tsc --noEmit` clean.
- Playwright: `notes-inbox.spec.mjs` (1/1) and
  `notes-popup-touch-tap.spec.mjs` (2/2) green — both exercise the
  send-note dialog rendering. `notes-popup-on-receive.spec.mjs` runs
  two browser contexts and exceeds the local 120s shell cap; not
  re-run here, but the diff is CSS-only and cannot affect the wire
  flow it covers.

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

@@ -1644,20 +1644,19 @@ function SendNoteDialog({
   return (
     <Dialog open onOpenChange={(o) => !o && onClose()}>
       <DialogContent className="max-w-md" data-testid="send-note-dialog">
-        <DialogHeader>
+        <DialogHeader className="pe-8">
           <DialogTitle>{t("notes.sendNote", "Send note")}</DialogTitle>
         </DialogHeader>
         <div className="relative">
           <Search
             size={14}
-            className="absolute top-1/2 -translate-y-1/2 text-muted-foreground"
-            style={lang === "ar" ? { right: 10 } : { left: 10 }}
+            className="absolute top-1/2 -translate-y-1/2 text-muted-foreground start-2.5"
           />
           <Input
             value={search}
             onChange={(e) => setSearch(e.target.value)}
             placeholder={t("notes.recipientsPlaceholder", "Search people…")}
-            className={lang === "ar" ? "pe-9" : "ps-9"}
+            className="ps-9"
             data-testid="send-note-search"
           />
         </div>