Implement soft keyboard visibility on Android

- Added `SoftKeyboardContext` enum and support for calculating keyboard
  insets from both virtual and platform sources

- Updated `AppContext` to provide `soft_keyboard_rect` for determining
  visible keyboard area

- Adjusted UI rendering to shift content when input boxes intersect with
  the soft keyboard, preventing overlap

- Modified `MainActivity` and Android manifest to use
  `windowSoftInputMode="adjustResize"` and updated window inset handling

- Introduced helper functions (`include_input`, `input_rect`,
  `clear_input_rect`) in `notedeck_ui` for tracking focused input boxes

- Fixed Android JNI keyboard height reporting to clamp negative values

Together, these changes allow the app to correctly detect and respond
to soft keyboard visibility on Android, ensuring input fields remain
accessible when typing.

Fixes: https://github.com/damus-io/notedeck/issues/946
Fixes: https://github.com/damus-io/notedeck/issues/1043

crates/notedeck_ui/src/lib.rs

@@ -62,3 +62,34 @@ pub fn secondary_label(ui: &mut egui::Ui, s: impl Into<String>) -> egui::Respons
     let color = ui.style().visuals.noninteractive().fg_stroke.color;
     ui.add(Label::new(RichText::new(s).size(10.0).color(color)).selectable(false))
 }
+
+const INPUT_RECT_KEY: &str = "notedeck_input_rect";
+
+/// Includes an input rect for keyboard visibility purposes. We use this to move the screen up if
+/// a soft keyboard intersects with the input box
+pub fn include_input(ui: &mut egui::Ui, resp: &egui::Response) {
+    // only include input if we have focus
+    if !resp.has_focus() {
+        return;
+    }
+
+    ui.data_mut(|d| {
+        let id = egui::Id::new(INPUT_RECT_KEY);
+        match d.get_temp::<egui::Rect>(id) {
+            Some(r) => d.insert_temp(id, resp.rect.union(r)),
+            None => d.insert_temp(id, resp.rect),
+        }
+    })
+}
+
+/// Set the last input rect for keyboard visibility purposes. We use this to move the screen up if
+/// a soft keyboard intersects with the input box
+pub fn input_rect(ui: &mut egui::Ui) -> Option<egui::Rect> {
+    ui.data(|d| d.get_temp(egui::Id::new(INPUT_RECT_KEY)))
+}
+
+/// Set the last input rect for keyboard visibility purposes. We use this to move the screen up if
+/// a soft keyboard intersects with the input box
+pub fn clear_input_rect(ui: &mut egui::Ui) {
+    ui.data_mut(|d| d.remove::<egui::Rect>(egui::Id::new(INPUT_RECT_KEY)))
+}