fix#14287fix#15359fix#15424
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## Summary by CodeRabbit
* **New Features**
* Redesigned workspace AI provider settings with connection testing,
storage options, model selection, capability management, ordering, and
custom endpoints.
* AI chat model choices now adapt to the selected workspace and
conversation route.
* Added support for image-based AI requests.
* **Bug Fixes**
* Improved handling of unavailable or outdated model selections.
* App configuration updates now reject overlapping paths and load
deterministically.
* **Tests**
* Expanded coverage for provider models, AI chat scoping, image
requests, and configuration validation.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->