Update README with config endpoints

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

README.md

@@ -43,6 +43,46 @@ Interactive docs: http://localhost:8100/docs
 | POST | `/cache/import?path=` | Import local file to cache |
 | POST | `/cache/upload` | Upload file to cache |
 | GET | `/assets` | List known assets |
+| POST | `/configs/upload` | Upload a config YAML |
+| GET | `/configs` | List configs |
+| GET | `/configs/{id}` | Get config details |
+| DELETE | `/configs/{id}` | Delete a config |
+| POST | `/configs/{id}/run` | Run a config |
+
+### Configs
+
+Configs are YAML files that define reusable DAG pipelines. They can have:
+- **Fixed inputs**: Assets with pre-defined content hashes
+- **Variable inputs**: Placeholders filled at run time
+
+Example config:
+```yaml
+name: my-effect
+version: "1.0"
+description: "Apply effect to user image"
+
+registry:
+  effects:
+    dog:
+      hash: "abc123..."
+
+dag:
+  nodes:
+    - id: user_image
+      type: SOURCE
+      config:
+        input: true        # Variable input
+        name: "input_image"
+
+    - id: apply_dog
+      type: EFFECT
+      config:
+        effect: dog
+      inputs:
+        - user_image
+
+  output: apply_dog
+```
 
 ### Start a run