Tag every AI Media request for Drupal AI Logging and observability

Problem/Motivation

AI Media requests reach Drupal AI without tags, so AI Logging and AI Observability cannot tell them apart from other AI calls on the site, or show usage per generator.

Steps to reproduce

1. Enable AI Logging.
2. Generate an image and an SVG.
3. The log entries carry no AI Media tags.

Proposed resolution

• Tag each request with ai_media, ai_media:<generator> and the step (generate, name, alt, description), through the provider's setTag().
• Document how to filter AI Logging by these tags.
• Kernel test.

AI-Generated: Yes

Remaining tasks

• ✅ File an issue
• ❌ Addition/Change/Update/Fix
• ❌ Testing to ensure no regression
• ❌ Automated unit/functional testing coverage
• ❌ Developer Documentation support
• ❌ User Guide Documentation support
• ➖ UX/UI designer responsibilities
• ➖ Accessibility and Readability
• ❌ Reviewed by a human
• ❌ Code review by maintainers
• ❌ Full testing and approval
• ❌ Credit contributors
• ❌ Review with the product owner
• ❌ Update Release Notes
• ❌ Release

User interface changes

• None.

API changes

• None.

Data model changes

• None.

Release notes snippet

• N/A