Keep keyboard offsets tied to visibility

Derive app keyboard offsets from one provider-owned shared value so chat content, composer surfaces, and floating panels share the same policy.

Treat progress-zero keyboard samples as closed, even if Android reports a stale nonzero height.

packages/app/src/hooks/keyboard-shift-policy.ts

@@ -0,0 +1,23 @@
+export const DEFAULT_IOS_KEYBOARD_INSET_MIN_HEIGHT = 120;
+
+export function resolveKeyboardShift(input: {
+  rawKeyboardHeight: number;
+  keyboardProgress: number;
+  bottomInset: number;
+  isIos: boolean;
+  iosMinHeight: number;
+}): number {
+  "worklet";
+
+  if (!(input.keyboardProgress > 0) || !(input.rawKeyboardHeight > 0)) {
+    return 0;
+  }
+
+  // iOS can report a small accessory/prediction bar height during touch focus.
+  // Treat that as non-keyboard so layouts don't "bounce" while interacting.
+  if (input.isIos && input.rawKeyboardHeight < input.iosMinHeight) {
+    return 0;
+  }
+
+  return Math.max(0, input.rawKeyboardHeight - input.bottomInset);
+}