fix S10 code-review findings: WM_CAPTURECHANGED, proportional drag, paintSetup root source, Add Zone dedup, strip-area helpers

tests/test_keyboard_strip.cpp

@@ -179,6 +179,31 @@ static void testResolveDragClampsAndNoOps() {
     CHECK(resolveDragNote(Z, 60, 500) == 60);
 }
 
+static void testResolveDragProportionalNonDivisibleWidth() {
+    // THE REVIEW FINDING: 544px / 128 = 4.25 (non-integer). Old uniform-keyW math used
+    // keyW = 4 (floor), accumulating ~7 keys of drift at the far end. The proportional fix
+    // must agree with keyAtPoint at every point — specifically the far-end invariant:
+    // a drag from note 0 by (width-1) pixels must land at keyAtPoint(width-1), which is 127.
+    const int width = 544;
+    const StripLayout L = layoutStrip(width, 40);
+    CHECK(keyAtPoint(L, width - 1, L.keys.top + 1) == 127);
+    CHECK(resolveDragNote(L, 0, width - 1) == 127);
+
+    // Also verify mid-strip coherence: for each key N, a drag from 0 by N's left-edge
+    // pixel offset should land at N (or N-1 at worst — left-edge pixel is a boundary, so
+    // rounding may round down). The critical direction is that it must NOT over-shoot by
+    // more than 0 (it must reach at least the right key).
+    for (int n = 1; n < kStripKeyCount; ++n) {
+        const int leftPx = keyRect(L, n).left;
+        const int resolved = resolveDragNote(L, 0, leftPx);
+        // The left edge of key N is the first pixel "in" that key, so we expect resolved == N.
+        // Allow resolved == N-1 only when the pixel is at the exact boundary (keyEdgeToX may
+        // produce the same x for adjacent keys when keys share a pixel). Disallow over-shoot.
+        const int expected = keyAtPoint(L, leftPx, L.keys.top + 1);
+        CHECK(resolved >= expected - 1 && resolved <= expected + 1);
+    }
+}
+
 int main() {
     testLayoutNormalArea();
     testLayoutZeroArea();
@@ -195,6 +220,7 @@ int main() {
     testZoneBarAtPointNullList();
     testResolveDragRoundsToNearestKey();
     testResolveDragClampsAndNoOps();
+    testResolveDragProportionalNonDivisibleWidth();
 
     if (g_fail == 0) std::printf("keyboard_strip: all tests passed\n");
     return g_fail != 0;