fix(tui): correct CHROME_ROWS (8→10) and clip frame to terminal height

CHROME_ROWS undercounted by 2 — column headers and separator inside
renderAgentList() were not budgeted. This caused render() to produce
rows+2 lines, and flush() wrote them all, scrolling the terminal and
creating visual line duplication on cursor movement.

Three layers of defense:
- CHROME_ROWS = 10 (root cause)
- flush() clips nextLines to process.stdout.rows (both diff and full-redraw paths)
- render() clips output to rows after bottom border

Author: dmicheneau

src/tui/renderer.mjs

@@ -727,6 +727,8 @@ export function render(state) {
 
   // Bottom border
   out.push(botBorder(cols));
+  // Clip to terminal height — safety net against chrome miscount
+  if (out.length > rows) out.length = rows;
 
   return out.join('\n');
 }

src/tui/screen.mjs

@@ -89,12 +89,13 @@ export function exit() {
  * @param {string} buffer - Complete frame content.
  */
 export function flush(buffer) {
-  const nextLines = buffer.split('\n');
+  const nextLines = buffer.split('\n').slice(0, process.stdout.rows);
+  const clipped = nextLines.join('\n');
   let out = SYNC_START;
 
   if (nextLines.length !== prevLines.length) {
     // Line count changed — full redraw
-    out += CURSOR_HOME + buffer + CLEAR_TO_END;
+    out += CURSOR_HOME + clipped + CLEAR_TO_END;
   } else {
     // Diff: only repaint changed lines
     for (let i = 0; i < nextLines.length; i++) {

src/tui/state.mjs

@@ -9,7 +9,7 @@ import { getWarningsForPreset, getWarningsForPermission } from '../permissions/w
 
 // ─── Constants ───────────────────────────────────────────────────────────────
 
-const CHROME_ROWS = 8;
+const CHROME_ROWS = 10;
 const MIN_VIEWPORT = 5;
 
 // ─── Types (JSDoc) ───────────────────────────────────────────────────────────

tests/tui.test.mjs

@@ -1120,7 +1120,7 @@ describe('getViewportHeight', () => {
   it('returns rows minus chrome, at least MIN_VIEWPORT', () => {
     const state = makeState({}, { cols: 80, rows: 24 });
     const vh = getViewportHeight(state);
-    assert.equal(vh, 24 - 8); // rows - CHROME_ROWS
+    assert.equal(vh, 24 - 10); // rows - CHROME_ROWS
   });
 
   it('clamps to MIN_VIEWPORT for small terminals', () => {