Add OpenAI-compatible model client

docs/policy/architecture.md

@@ -21,7 +21,7 @@ The implemented internal components consist of:
 - `internal/domain`, which owns framework data values shared by later internal
   components;
 - `internal/defaults`, which owns application-neutral framework defaults and
-  constructs the default execution target; and
+  constructs the default execution target;
 - `internal/filecatalog`, which discovers YAML files and provides source-path
   helpers for filesystem and `fs.FS` consumers;
 - `internal/promptdef`, which loads and validates prompt definitions from
@@ -32,17 +32,20 @@ The implemented internal components consist of:
   catalog;
 - `internal/prompt`, which renders prompt messages from Go templates;
 - `internal/artifact`, which resolves ordinary inline and unrestricted
-  caller-selected file references; and
+  caller-selected file references;
 - `internal/validate`, which validates basic, JSON, and JSON Schema output
-  using filesystem and `fs.FS` schema sources.
+  using filesystem and `fs.FS` schema sources; and
+- `internal/llm`, which defines the provider-neutral generation boundary and
+  implements outbound OpenAI-compatible chat requests.
 
 The defaults and renderer depend on the domain model. Prompt-definition and
 profile repositories use the domain model, file catalog, and YAML decoder. The
 built-in profile repository supplies an embedded `fs.FS` to the profile
 package. Artifact reading uses the domain model and application-neutral
 defaults. Validation uses the domain model, file catalog, and JSON Schema
-implementation. Model clients, orchestration, and the public engine have not
-yet been extracted.
+implementation. The model client uses the domain model, application-neutral
+defaults, and an injected or standard-library HTTP client. Orchestration and
+the public engine have not yet been extracted.
 
 Future framework extraction must follow this dependency direction: