Document the model capability system

AGENTS.md

@@ -155,7 +155,8 @@ Key structure:
 Plugins are written in Lua and provide:
 - **Language plugins** - I18N translations (e.g., German language pack)
 - **Configuration plugins** - Enterprise IT configurations for centrally managed providers, settings
-- **Future:** Assistant plugins for custom assistants
+- **Assistant plugins** - custom assistants and direct-chat launchers, subject to approval or a local security audit
+- **Model plugins** - what an organization's own models can do, see `documentation/Models.md`
 
 **Example configuration plugin:** `app/MindWork AI Studio/Plugins/configuration/plugin.lua`
 
@@ -191,6 +192,21 @@ When adding, changing, or removing model-driven tools, keep these parts in sync:
 
 Tool implementations must treat model-provided arguments as untrusted input. Validate settings and arguments, protect secrets with `SensitiveTraceArgumentNames`, use `ToolExecutionBlockedException` for intentional policy blocks, and check provider confidence before returning sensitive data to the model.
 
+## Model Capabilities
+
+**Documentation:** `documentation/Models.md`
+
+What a model can do is answered in `app/MindWork AI Studio/Models/`, through `provider.GetModelProfile()`. Never ask `ModelRegistry` directly from a component: the extension method is what adds the expert settings and what a provider's model list reported, and the registry alone answers neither.
+
+When adding, changing, or removing model knowledge, keep these parts in sync:
+- `app/MindWork AI Studio/Models/<Vendor>/<Family>.cs` for the family itself. Creating the class is enough — the source generator in `app/SourceGeneratedMappings/` collects every non-abstract `ModelFamily` and `IModelHost` at compile time, so there is no registration list. Do not add reflection here; `PublishTrimmed` is on.
+- `app/Tests/Models/Corpus/` for the model IDs the family covers, marked as either unchanged or expected to change. A porting difference which nobody declared is what the corpus exists to catch.
+- `app/MindWork AI Studio/Models/Kinds/` when the change is about what kind of model something is, rather than what it can do. These are ordinary rules of the same engine.
+- `app/MindWork AI Studio/Models/Hosting/Hosts/` when a provider wraps model names or cannot pass an API through. A host unwraps and trims the transport; it states nothing about the model itself.
+- `app/MindWork AI Studio/Plugins/models/plugin.lua` when a new field can be declared by an organization, and `app/MindWork AI Studio/Plugins/configuration/plugin.lua` when it can be overridden per provider instance.
+
+Rules are never tried in order: specificity is computed from the rule, and two rules of equal specificity on one name fail the test suite. State how a model reasons with `Reasoning(...)` — the three reasoning capabilities are override vocabulary and must never appear in a profile. Every family and every host has to name the page it was read from and the day somebody read it; `dotnet run verify-models` reports the ones which have gone stale.
+
 ## RAG (Retrieval-Augmented Generation)
 
 RAG integration is currently in development (preview feature). Architecture: