fix(input): remove z-index target-area for ionic theme (#30261)

Issue number: internal
---------

## What is the current behavior?
Currently, operations associated with gestures aren’t working, for the
ionic theme:
- can’t select the text using double tap
- can’t longpress
- can’t move the cursor to any positions

## What is the new behavior?
- It's now possible to select text using double tap, long press and move
the cursor to different positions
- Adds new tests for double clicks

| Before | Now |
|--------|-----|

|![prev](https://github.com/user-attachments/assets/c1c54710-e534-44bf-9ef9-6ddc990996d9)
|
![now](https://github.com/user-attachments/assets/b10b8696-e0bb-4e99-9d3d-fe5a92d384e8)
|

## Does this introduce a breaking change?
- [ ] Yes
- [x] No

## Notes
Currently, the double click text selection is not working (the text
isn't selected) on the automated tests for:
- ionic theme, on firefox and safari
- md/ios themes, on firefox

as manual tests do not have this problem, we'll be skipping these tests
for now and come back to them at a later date

---------

Co-authored-by: Maria Hutt <thetaPC@users.noreply.github.com>

core/src/components/input/input.ionic.scss

@@ -65,8 +65,6 @@
 
   // Cursor should match the native input when hovering over the target area.
   cursor: text;
-
-  z-index: 1;
 }
 
 ::slotted([slot="start"]),

core/src/components/input/test/basic/input.e2e.ts

@@ -29,7 +29,6 @@ configs().forEach(({ title, screenshot, config }) => {
         await expect(input).toHaveScreenshot(screenshot(`input-with-placeholder`));
       });
     });
-
     test.describe('input with clear button', () => {
       test('should not have visual regressions with default label', async ({ page }) => {
         await page.setContent(
@@ -63,6 +62,43 @@ configs().forEach(({ title, screenshot, config }) => {
         await expect(input).toHaveScreenshot(screenshot(`input-with-clear-button-stacked`));
       });
     });
+    test.describe('input click behaviors', () => {
+      test('should not have visual regressions when user double clicks', async ({ page }) => {
+        await page.setContent(
+          `
+          <ion-input
+            label="Label"
+            clear-input="true"
+            value="Text"
+          ></ion-input>
+        `,
+          config
+        );
+        const input = page.locator('ion-input');
+        const nativeInput = input.locator('input');
+        await nativeInput.dblclick();
+        // Validates the display of an input with a clear button.
+        await expect(input).toHaveScreenshot(screenshot(`input-dbclick`));
+      });
+      test('should not have visual regressions with stacked label when user double clicks', async ({ page }) => {
+        await page.setContent(
+          `
+          <ion-input
+            label="Label"
+            label-placement="stacked"
+            clear-input="true"
+            value="Text"
+          ></ion-input>
+        `,
+          config
+        );
+        const input = page.locator('ion-input');
+        const nativeInput = input.locator('input');
+        await nativeInput.dblclick();
+        // Validates the display of an input with a clear button.
+        await expect(input).toHaveScreenshot(screenshot(`input-dbclick-stacked`));
+      });
+    });
   });
 });
 
@@ -185,6 +221,24 @@ configs({ modes: ['ionic-md'] }).forEach(({ title, screenshot, config }) => {
       const container = page.locator('#container');
       await expect(container).toHaveScreenshot(screenshot(`input-clear-button-focused`));
     });
+
+    test('should not have visual regressions when user double clicks', async ({ page }) => {
+      await page.setContent(
+        `
+          <ion-input
+            label="Label"
+            label-placement="stacked"
+            clear-input="true"
+            value="Text"
+          ></ion-input>
+      `,
+        config
+      );
+      const input = page.locator('ion-input');
+      const nativeInput = input.locator('input');
+      await nativeInput.dblclick();
+      await expect(input).toHaveScreenshot(screenshot(`input-dbclick`));
+    });
   });
 });