Enable explicit configuration imports and overlays

examples/config-fragments/backend.yml

@@ -0,0 +1,4 @@
+backends:
+  local-gpu:
+    endpoint: http://localhost:11434/v1
+    api_key_env: LOCAL_GPU_API_KEY

examples/config-fragments/sources.yml

@@ -0,0 +1,3 @@
+prompt_dir: ./examples/prompts
+profile_dir: ./examples/profiles
+schema_dir: ./examples/schemas

examples/config.composed.yml

@@ -0,0 +1,8 @@
+# Select from the repository root; application paths remain working-directory-relative.
+configkit:
+  imports:
+    - path: config-fragments/sources.yml
+    - path: config-fragments/backend.yml
+
+server:
+  addr: :8080

examples/overlays/local.yml

@@ -0,0 +1,4 @@
+defaults:
+  render_format: json
+server:
+  addr: 127.0.0.1:8080