A GOOD MILESTONE : Refactor title bar and toolbar typography, improve tooltip styles, and enhance selection transform functionality

- Updated typography constants for menu bar and tooltips to improve readability and consistency.
- Adjusted button padding and widths in the title bar for better layout.
- Replaced tooltip implementation with a new balloon tooltip style for improved visual feedback.
- Enhanced selection transform logic to support rotation and resizing, ensuring accurate hit testing and bounds calculations.
- Added tests for selection clearing and transformed bounds to ensure functionality and prevent regressions.
- Introduced a new module for managing selection transform dirty bounds during interactive previews.

hcie-engine-api/tests/selection_clear.rs

@@ -0,0 +1,54 @@
+//! Selection pixel-clearing regression tests.
+//!
+//! **Purpose:** Verifies that destructive selection operations use the active
+//! document selection mask rather than the brush stroke's temporary mask cache.
+//!
+//! **Logic & Workflow:** Each test creates an opaque raster layer through the
+//! public engine API, installs a deterministic selection mask, clears selected
+//! pixels, and compares alpha values inside and outside that mask.
+//!
+//! **Side Effects / Dependencies:** Uses only in-memory `hcie-engine-api` state;
+//! no files, network services, GUI runtime, or engine internals are accessed.
+
+use hcie_engine_api::Engine;
+
+/// Confirms that selection clearing removes internal pixels and preserves all
+/// pixels external to the selection.
+///
+/// **Purpose:** Prevents a regression where `clear_selection_pixels` consulted
+/// an empty stroke cache and consequently cleared the complete active layer.
+///
+/// **Logic & Workflow:** Creates a 3×3 opaque layer, selects only its center
+/// pixel, invokes selection clearing, then checks every resulting alpha value.
+///
+/// **Arguments & Returns:** Takes no arguments and returns nothing; assertion
+/// failures report whether an internal or external pixel was handled wrongly.
+///
+/// **Side Effects / Dependencies:** Mutates only the local in-memory engine and
+/// records the normal undo snapshot generated by the clear operation.
+#[test]
+fn clear_selection_pixels_clears_inside_and_preserves_outside() {
+    let mut engine = Engine::new(3, 3);
+    engine.set_active_layer_pixels(vec![255; 3 * 3 * 4]);
+
+    let mut mask = vec![0; 3 * 3];
+    mask[4] = 255;
+    engine.set_selection_mask(mask);
+
+    engine.clear_selection_pixels();
+
+    let pixels = engine
+        .get_active_layer_pixels()
+        .expect("a new engine must have an active raster layer");
+    for pixel_index in 0..9 {
+        let alpha = pixels[pixel_index * 4 + 3];
+        if pixel_index == 4 {
+            assert_eq!(alpha, 0, "selected center pixel must be cleared");
+        } else {
+            assert_eq!(
+                alpha, 255,
+                "unselected pixel {pixel_index} must be preserved"
+            );
+        }
+    }
+}