docs(video): document runway support

docs/providers/runway.md

@@ -0,0 +1,67 @@
+---
+title: "Runway"
+summary: "Runway video generation setup in OpenClaw"
+read_when:
+  - You want to use Runway video generation in OpenClaw
+  - You need the Runway API key/env setup
+  - You want to make Runway the default video provider
+---
+
+# Runway
+
+OpenClaw ships a bundled `runway` provider for hosted video generation.
+
+- Provider: `runway`
+- Auth: `RUNWAYML_API_SECRET` (canonical; `RUNWAY_API_KEY` also works)
+- API: Runway task-based video generation API
+
+## Quick start
+
+1. Set the API key:
+
+```bash
+openclaw onboard --auth-choice runway-api-key
+```
+
+2. Set a default video model:
+
+```json5
+{
+  agents: {
+    defaults: {
+      videoGenerationModel: {
+        primary: "runway/gen4.5",
+      },
+    },
+  },
+}
+```
+
+## Video generation
+
+The bundled `runway` video-generation provider defaults to `runway/gen4.5`.
+
+- Modes: text-to-video, single-image image-to-video, and single-video video-to-video
+- Runtime: async task submit + poll via `GET /v1/tasks/{id}`
+- Local image/video references: supported via data URIs
+- Current video-to-video caveat: OpenClaw currently requires `runway/gen4_aleph` for video inputs
+- Current text-to-video caveat: OpenClaw currently exposes `16:9` and `9:16` for text-only runs
+
+To use Runway as the default video provider:
+
+```json5
+{
+  agents: {
+    defaults: {
+      videoGenerationModel: {
+        primary: "runway/gen4.5",
+      },
+    },
+  },
+}
+```
+
+## Related
+
+- [Video Generation](/tools/video-generation)
+- [Configuration Reference](/gateway/configuration-reference#agent-defaults)