Copy and layout updates on context item scope form
## Problem/motivation
Follow-up to:
#3586196+s
**_Note that some of these things may have already been implemented in separate issues._**
The **Context Scope** section on the context item edit form needs a few small copy and layout tweaks: clearer help text, less clutter, and a more logical order for the summary badges.
No matching logic or scope model changes — just form presentation.
## Solution
### Context item form
- [x] Remove the **Context Scope Settings** link from the section description.
- [x] Update the section description to:
> Control when this context item is included. Add multiple scopes to include it whenever any one matches, or turn on Global context to always include it.
- [x] Ensure **Global context** help text reads:
> Always include this context for every agent. Saving with this on will clear the scope settings below.
Check [#3586214](https://git.drupalcode.org/project/ai_context/-/work_items/3586214) first — global copy may already be updated there.
- [x] Remove **“Leave empty to ignore.”** from the global control, if still present.
- [x] Move the **scope summary** badges below the Global context toggle.
- [x] Hide the scope summary when Global context is selected.
## Out of scope
Other things handled in: #3586281+s
- Filter/AND semantics (e.g., Language)
- Agent subscription form changes
- Selection logic changes
- Two-tier “Match any” / “Filter by” UI
## Test plan
1. Add or edit a context item at `/admin/config/ai/context/items`.
2. Confirm updated section description and global help text; no settings link in the description.
3. Select several scopes — summary appears **below** Global and shows the right badges.
4. Enable **Global context** — summary and other scope fields are hidden.
issue