fix(toolbar): MD height only applies to MD segment (#26042)

resolves #18617

Co-authored-by: brandyscarney <brandyscarney@users.noreply.github.com>

core/src/components/segment/segment.md.scss

@@ -8,10 +8,23 @@
   --background: transparent;
 }
 
+// Segment: In Toolbar
+// --------------------------------------------------
+
+:host(.in-toolbar) {
+  /**
+   * Segment should inherit the
+   * height of the toolbar.
+   * Note: --min-height is initially
+   * set on ion-toolbar, not ion-segment
+   */
+  min-height: var(--min-height);
+}
+
 
 // Segment: Scrollable
 // --------------------------------------------------
 
 :host(.segment-scrollable) ::slotted(ion-segment-button) {
   min-width: auto;
-}
+}

core/src/components/segment/test/toolbar/segment.e2e.ts

@@ -38,5 +38,33 @@ test.describe('segment: toolbar', () => {
 
       expect(await header.screenshot()).toMatchSnapshot(`segment-toolbar-color-${page.getSnapshotSettings()}.png`);
     });
+
+    test('should not inherit height when segment is MD and toolbar is iOS', async ({ page, skip }) => {
+      skip.rtl();
+      skip.mode('ios', 'We manually set the mode in this test, so the automatic mode switching is not needed');
+
+      test.info().annotations.push({
+        type: 'issue',
+        description: 'https://github.com/ionic-team/ionic-framework/issues/18617',
+      });
+
+      await page.setContent(`
+        <ion-header>
+          <ion-toolbar mode="ios" color="primary">
+            <ion-segment mode="md" value="a">
+              <ion-segment-button value="a">First</ion-segment-button>
+              <ion-segment-button value="b">Second</ion-segment-button>
+              <ion-segment-button value="c" disabled="true">Third</ion-segment-button>
+            </ion-segment>
+          </ion-toolbar>
+        </ion-header>
+      `);
+
+      const header = page.locator('ion-header');
+
+      expect(await header.screenshot()).toMatchSnapshot(
+        `segment-toolbar-height-inherit-${page.getSnapshotSettings()}.png`
+      );
+    });
   });
 });