Just a tiny nit i came across - realised that if the schema is not
exposed via the API, the warning that we show on the policies page RE
data not being selectable is repeated for each table which imo seems
unnecessary.
Opting for a single admonition at the top instead
## Before
<img width="1085" height="744" alt="image"
src="https://github.com/user-attachments/assets/7bd8cf7b-f5a8-47d6-b41f-13fc4782ed8b"
/>
### After
<img width="1080" height="673" alt="image"
src="https://github.com/user-attachments/assets/c839f502-42ff-4184-ad07-0ff2fd2d2676"
/>
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **New Features**
* Added an on-screen warning for tables whose schemas aren’t exposed via
the project Data APIs, including a link to Data API settings.
* **UI Improvements**
* Refined the “filter entity types” control’s tooltip behavior and
updated the popover header text.
* **Bug Fixes**
* Improved Data API/RLS status messaging by removing the prior “schema
not exposed” outcome and showing “unknown” when access can’t be
determined.
* Consolidated policy warning rendering to avoid duplicated or
inconsistent messages.
* **Tests**
* Updated policy/admonition helper tests to match the revised status and
message behavior.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
