fix(mobile): do not dismiss the keyboard when a scroll ends

Regression from the dismiss handler in #279: it fired on any touchend,
and a scroll ends in touchend too. Scrolling to read something while composing
closed the keyboard and dropped the composer — worse than the bug it fixed.

Track finger travel from touchstart and only treat a near-stationary gesture as
a tap, using the same 8px TAP_THRESHOLD the terminal's own touch handling uses
so both agree on tap-vs-scroll. Multi-touch is never a dismissing tap.

All three listeners stay passive; nothing calls preventDefault.

Measured on a Pixel-class viewport with a Firefox UA:
  tap                -> dismissed
  scroll (120px)     -> keyboard kept
  micro-drift (4px)  -> dismissed, so an imprecise tap still works

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/web/public/terminal-ui.js

@@ -36,6 +36,9 @@
   // (_installMobileKeyboardDismiss). Two groups: anything that is about to take
   // focus itself, and the accessory bar, which is built to be used while the
   // keyboard is open.
+  // Finger travel (px) still counted as a tap for keyboard dismissal. Matches
+  // the terminal's own TAP_THRESHOLD so both agree on tap-vs-scroll.
+  const MOBILE_KEYBOARD_DISMISS_TAP_SLOP = 8;
   const MOBILE_KEYBOARD_DISMISS_EXEMPT_SELECTOR = [
     'input',
     'textarea',
@@ -199,6 +202,7 @@
     PAGE_KEY_MAX_PER_BATCH,
     TUI_PROMPT_DEFAULT_ROWS_FROM_BOTTOM,
     MOBILE_KEYBOARD_DISMISS_EXEMPT_SELECTOR,
+    MOBILE_KEYBOARD_DISMISS_TAP_SLOP,
   };
   global.CODEMAN_XTERM_THEMES = CODEMAN_XTERM_THEMES;
   global.codemanCurrentXtermTheme = currentXtermTheme;
@@ -3534,7 +3538,35 @@ Object.assign(CodemanApp.prototype, {
    */
   _installMobileKeyboardDismiss() {
     if (this._mobileKeyboardDismissHandler) return;
+
+    // A SCROLL also ends in touchend, and dismissing there is wrong: scrolling
+    // to read something while composing must not close the keyboard and lose
+    // the composer. Track how far the finger travelled and only treat a
+    // near-stationary gesture as a tap — the same TAP_THRESHOLD the terminal's
+    // own touch handling uses, so both agree on what a tap is.
+    let startX = 0;
+    let startY = 0;
+    let moved = false;
+    this._mobileKeyboardDismissStart = (ev) => {
+      if (ev.touches.length !== 1) {
+        moved = true; // a multi-touch gesture is never a dismissing tap
+        return;
+      }
+      startX = ev.touches[0].clientX;
+      startY = ev.touches[0].clientY;
+      moved = false;
+    };
+    this._mobileKeyboardDismissMove = (ev) => {
+      if (moved || !ev.touches.length) return;
+      const dx = ev.touches[0].clientX - startX;
+      const dy = ev.touches[0].clientY - startY;
+      const slop = window.CodemanTerminalInput.MOBILE_KEYBOARD_DISMISS_TAP_SLOP;
+      if (Math.abs(dx) > slop || Math.abs(dy) > slop) {
+        moved = true;
+      }
+    };
     this._mobileKeyboardDismissHandler = (ev) => {
+      if (moved) return;
       if (!this._isMobileTerminalInputFocused()) return;
       const target = ev.target;
       if (!target || typeof target.closest !== 'function') return;
@@ -3542,8 +3574,10 @@ Object.assign(CodemanApp.prototype, {
       if (target.closest(window.CodemanTerminalInput.MOBILE_KEYBOARD_DISMISS_EXEMPT_SELECTOR)) return;
       this._blurMobileTerminalInput();
     };
-    // Passive: this never calls preventDefault, so it must not make the page
+    // Passive throughout: this never calls preventDefault, so it must not make
-    // feel less responsive to scrolling.
+    // the page feel less responsive to scrolling.
+    document.addEventListener('touchstart', this._mobileKeyboardDismissStart, { passive: true });
+    document.addEventListener('touchmove', this._mobileKeyboardDismissMove, { passive: true });
     document.addEventListener('touchend', this._mobileKeyboardDismissHandler, { passive: true });
   },