chore(studio): use sentence case for Data API access label (#47353)

## What kind of change does this PR introduce?

UI copy + agent guidance.

## What is the current behavior?

- The Table Editor labels the Data API setting as "Data API Access"
(title case).
-  Agents have no scoped pointer to our copywriting rules

## What is the new behavior?

- Label uses sentence case: "Data API access" (e2e and test docs
updated).
- Agents are pointed at
`apps/design-system/content/docs/copywriting.mdx` via
`studio-copy.instructions.md` and `studio-ui-patterns` skill.

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Bug Fixes**
* Standardized the **“Data API access”** label casing across the Studio
UI.
  * Updated end-to-end tests to assert the corrected label text.
* **Documentation**
* Updated Studio E2E test review instructions and examples to use
**“Data API access”**.
* Added/expanded Studio UI copywriting guidance, including where to
source copy and how to apply consistent casing.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: Cursor <cursoragent@cursor.com>

e2e/studio/features/api-access-toggle.spec.ts

@@ -57,14 +57,14 @@ async function verifyTablePrivileges(
 }
 
 /**
- * Locates the API access toggle switch for Data API Access.
+ * Locates the API access toggle switch for Data API access.
  * Only present when creating or duplicating a table (not when editing).
  */
 function getApiAccessSwitch(page: Page) {
   const sidePanel = page.getByTestId('table-editor-side-panel')
   const dataApiSection = sidePanel
     .locator('div')
-    .filter({ hasText: 'Data API Access' })
+    .filter({ hasText: 'Data API access' })
     .filter({ has: page.getByRole('switch') })
   return dataApiSection.getByRole('switch')
 }
@@ -239,10 +239,10 @@ test.describe('API Access Toggle', () => {
     await page.getByRole('menuitem', { name: 'Edit table' }).click()
     await expect(page.getByTestId('table-editor-side-panel')).toBeVisible()
 
-    // Data API Access section is visible
+    // Data API access section is visible
     await expect(
-      page.getByText('Data API Access'),
-      'Data API Access label should be visible in edit mode'
+      page.getByText('Data API access'),
+      'Data API access label should be visible in edit mode'
     ).toBeVisible()
 
     // In edit mode the panel shows a "Manage access" link instead of a toggle switch