docs: add module documentation in AsciiDoc with PlantUML diagrams

Generated by per-group subagents covering all 52 modules across:
core (18), infrastructure (10), apps (5), interfaces (3),
plugins (7), testing (9)

Documentation format:
- AsciiDoc (.adoc) files in docs/modules/<group>/
- PlantUML (.puml) files in docs/diagrams/
- .adoc files reference diagrams via include:: directives

Each doc covers: purpose, responsibilities, non-responsibilities,
key types, event flow, integration points, invariants, PlantUML
diagram, known issues, and open questions.

docs/modules/infrastructure/infra-inference-commons.adoc

@@ -0,0 +1,78 @@
+= infra-inference-commons
+
+== purpose
+
+Defines shared abstractions and types for inference provider lifecycle management. Provides the `ModelManager` interface for loading/unloading models, the `ManagedInferenceProvider` wrapper that ties an `InferenceProvider` to a model lifecycle, and supporting types (`ModelDescriptor`, `ResidencyMode`, `ModelLoadException`).
+
+== responsibilities
+
+* Define the contract for model lifecycle management (load, unload, health check)
+* Provide a managed wrapper around `InferenceProvider` that supports model replacement
+* Define residency modes that govern when models are unloaded (persistent, dynamic, ephemeral)
+* Describe model configuration via `ModelDescriptor`
+
+== non-responsibilities
+
+* Does not implement any inference provider — that belongs to `infra:inference:llama-cpp` and similar
+* Does not handle provider routing or selection
+* Does not define the core inference contract — that belongs to `core:inference`
+
+== key types
+
+=== ModelManager
+* **kind**: interface
+* **purpose**: Contract for loading, unloading, and health-checking inference models. Enforces single-model-at-a-time.
+* **methods**: `load(descriptor)`, `unload(modelId)`, `currentModel()`, `healthCheck()`
+
+=== ManagedInferenceProvider
+* **kind**: interface
+* **purpose**: Extends `InferenceProvider` with lifecycle management (unload, isLoaded, load a different model).
+* **methods**: `unload()`, `isLoaded()`, `load(newDescriptor)`
+
+=== ModelDescriptor
+* **kind**: data class
+* **purpose**: Describes a model instance with its path, residency mode, context size, and capabilities.
+* **fields**: `modelId`, `modelPath`, `residencyMode`, `idleTimeoutMs` (default 60000), `contextSize` (default 8192), `capabilities`
+
+=== ResidencyMode
+* **kind**: enum class
+* **purpose**: Governs model unloading behavior.
+* **variants**: `PERSISTENT` (never unload), `DYNAMIC` (unload after idle timeout), `EPHEMERAL` (unload immediately after inference)
+
+=== ModelLoadException
+* **kind**: class
+* **purpose**: Exception thrown when model loading or unloading fails. Carries `modelId` and optional cause.
+* **fields**: `message`, `modelId`, `cause`
+
+== event flow
+
+*None.* The commons layer defines abstractions only; events are emitted by implementations.
+
+== integration points
+
+* `core:inference` — `InferenceProvider`, `ProviderHealth`, `CapabilityScore`
+
+== invariants
+
+* `ModelManager` enforces single-model-at-a-time via mutex in implementations
+* Model loading must succeed through health checks before the provider is returned
+* `ManagedInferenceProvider.load()` replaces the current model entirely
+
+== PlantUML diagram
+
+[plantuml, infra-inference-commons, "png"]
+----
+include::../../diagrams/infra-inference-commons.puml[]
+----
+
+
+
+
+== known issues
+
+* `ManagedInferenceProvider.load()` uses `as? ManagedInferenceProvider` safe cast — returns null then throws explicit `ModelLoadException`, not `ClassCastException`
+
+== open questions
+
+* Should `ModelManager` support multiple concurrent models for different sessions?
+* Should `ResidencyMode.DYNAMIC` have a configurable timeout per-model or per-manager?