refactor(tui): /clean pass on blitz closeout — trim comments, flatten logic

- normalizeStatusBar collapses to one ternary expression
- /statusbar slash hoists the toggle value and flattens the branch tree
- shift-tab yolo comment reduced to one line
- cursorLayout/offsetFromPosition lose paragraph-length comments
- appLayout collapses the three {!overlay.agents && …} into one fragment
- StatusRule drops redundant flexShrink={0} (Yoga default)
- server.py uses a walrus + frozenset and trims the compat helper

Net -43 LoC. 237 vitest + 46 pytest green, layouts unchanged.

ui-tui/src/components/appChrome.tsx

@@ -191,7 +191,7 @@ export function StatusRule({
   const leftWidth = Math.max(12, cols - cwdLabel.length - 3)
 
   return (
-    <Box flexShrink={0} height={1}>
+    <Box height={1}>
       <Box flexShrink={1} width={leftWidth}>
         <Text color={t.color.bronze} wrap="truncate-end">
           {'─ '}