[Security Solution][Bug] Timeline: ESQL query editor showing on fullScreen mode (#242027)

## Summary

Fixes UI breaking when displaying **ESQL queries** in **Timeline full
screen mode**.

Closes #225998

## 🛑 Problem

When opening **Timeline** in full screen mode with an **ESQL query**
(for example, one added from the **AI Assistant**), the UI layout breaks
— some embedded **Discover** components (like `dscPageBody` or the
**ESQL editor**) interfere visually with Timeline elements.

## 💡 Solution

Added styling to correctly handle Discover’s full screen mode class
(`UNIFIED_DATA_TABLE_FULL_SCREEN_CLASS`).

Updated the TimelineESQLGlobalStyles to:

Hide the `.ESQLEditor` when the unified data table is full screen
This prevents layout conflicts between the embedded Discover components
and Timeline’s own full screen mode.

<details> <summary>Code change summary 🧩</summary>

- Imported `UNIFIED_DATA_TABLE_FULL_SCREEN_CLASS` from
`@kbn/unified-data-table/src/hooks/use_full_screen_watcher`

- Replaced hard-coded class selector `.unifiedDataTable__fullScreen`
with the imported constant

- Added visibility rules for `.ESQLEditor`

</details> <details> <summary>Screen recording / screenshot of fix
✅</summary>

[Paste your video or screenshot
here](https://github.com/user-attachments/assets/35fd54c8-3743-4a5d-9491-71b55e173c1a)

</details>

(cherry picked from commit 5805957)

Author: agusruidiazgd

x-pack/solutions/security/plugins/security_solution/public/timelines/components/timeline/tabs/esql/styles.tsx

@@ -6,6 +6,7 @@
  */
 
 import styled from '@emotion/styled';
+import { UNIFIED_DATA_TABLE_FULL_SCREEN_CLASS } from '@kbn/unified-data-table/src/hooks/use_full_screen_watcher';
 import { createGlobalStyle } from 'styled-components';
 
 export const EmbeddedDiscoverContainer = styled.div`
@@ -23,7 +24,10 @@ export const TimelineESQLGlobalStyles = createGlobalStyle`
   }
 
   // TODO this should be removed when we change the ES|QL tab to be our own component instead of Discover (hopefully 8.15)
-  .unifiedDataTable__fullScreen .dscPageBody * {
+  .${UNIFIED_DATA_TABLE_FULL_SCREEN_CLASS} .dscPageBody * {
     z-index: unset !important;
   }
+  .${UNIFIED_DATA_TABLE_FULL_SCREEN_CLASS} .ESQLEditor {
+    visibility: hidden;
+  }
 `;