Image generation: native provider migration and explicit capabilities (#49551)

* Docs: retire nano-banana skill wrapper

* Doctor: migrate nano-banana to native image generation

* Image generation: align fal aspect ratio behavior

* Image generation: make provider capabilities explicit

docs/tools/index.md

@@ -421,9 +421,24 @@ Notes:
 - Use `action: "list"` to inspect registered providers, default models, supported model ids, sizes, resolutions, and edit support.
 - Returns local `MEDIA:<path>` lines so channels can deliver the generated files directly.
 - Uses the image-generation model directly (independent of the main chat model).
-- Google-backed flows support reference-image edits plus explicit `1K|2K|4K` resolution hints.
+- Google-backed flows, including `google/gemini-3-pro-image-preview` for the native Nano Banana-style path, support reference-image edits plus explicit `1K|2K|4K` resolution hints.
 - When editing and `resolution` is omitted, OpenClaw infers a draft/final resolution from the input image size.
-- This is the built-in replacement for the old sample `nano-banana-pro` skill workflow. Use `agents.defaults.imageGenerationModel`, not `skills.entries`, for stock image generation.
+- This is the built-in replacement for the old `nano-banana-pro` skill workflow. Use `agents.defaults.imageGenerationModel`, not `skills.entries`, for stock image generation.
+
+Native example:
+
+```json5
+{
+  agents: {
+    defaults: {
+      imageGenerationModel: {
+        primary: "google/gemini-3-pro-image-preview", // native Nano Banana path
+        fallbacks: ["fal/fal-ai/flux/dev"],
+      },
+    },
+  },
+}
+```
 
 ### `pdf`
 

docs/tools/skills-config.md

@@ -42,6 +42,11 @@ For built-in image generation/editing, prefer `agents.defaults.imageGenerationMo
 plus the core `image_generate` tool. `skills.entries.*` is only for custom or
 third-party skill workflows.
 
+Examples:
+
+- Native Nano Banana-style setup: `agents.defaults.imageGenerationModel.primary: "google/gemini-3-pro-image-preview"`
+- Native fal setup: `agents.defaults.imageGenerationModel.primary: "fal/fal-ai/flux/dev"`
+
 ## Fields
 
 - `allowBundled`: optional allowlist for **bundled** skills only. When set, only