feat(baoyu-imagine): add Z.AI GLM-Image provider

Adds the Z.AI (智谱) provider supporting glm-image and cogview-4-250304
models via the Z.AI sync image API. Configure with ZAI_API_KEY (or
BIGMODEL_API_KEY for backward compat). Reference images are not supported yet.

skills/baoyu-imagine/references/config/preferences-schema.md

@@ -11,7 +11,7 @@ description: EXTEND.md YAML schema for baoyu-imagine user preferences
 ---
 version: 1
 
-default_provider: null      # google|openai|azure|openrouter|dashscope|minimax|replicate|null (null = auto-detect)
+default_provider: null      # google|openai|azure|openrouter|dashscope|zai|minimax|replicate|null (null = auto-detect)
 
 default_quality: null       # normal|2k|null (null = use default: 2k)
 
@@ -25,6 +25,7 @@ default_model:
   azure: null               # Azure deployment name, e.g., "gpt-image-1.5" or "image-prod"
   openrouter: null          # e.g., "google/gemini-3.1-flash-image-preview"
   dashscope: null           # e.g., "qwen-image-2.0-pro"
+  zai: null                 # e.g., "glm-image"
   minimax: null             # e.g., "image-01"
   replicate: null           # e.g., "google/nano-banana-pro"
 
@@ -49,6 +50,9 @@ batch:
     dashscope:
       concurrency: 3
       start_interval_ms: 1100
+    zai:
+      concurrency: 3
+      start_interval_ms: 1100
     minimax:
       concurrency: 3
       start_interval_ms: 1100
@@ -69,6 +73,7 @@ batch:
 | `default_model.azure` | string\|null | null | Azure default deployment name |
 | `default_model.openrouter` | string\|null | null | OpenRouter default model |
 | `default_model.dashscope` | string\|null | null | DashScope default model |
+| `default_model.zai` | string\|null | null | Z.AI default model |
 | `default_model.minimax` | string\|null | null | MiniMax default model |
 | `default_model.replicate` | string\|null | null | Replicate default model |
 | `batch.max_workers` | int\|null | 10 | Batch worker cap |
@@ -100,6 +105,7 @@ default_model:
   azure: "gpt-image-1.5"
   openrouter: "google/gemini-3.1-flash-image-preview"
   dashscope: "qwen-image-2.0-pro"
+  zai: "glm-image"
   minimax: "image-01"
   replicate: "google/nano-banana-pro"
 batch:
@@ -111,6 +117,9 @@ batch:
     azure:
       concurrency: 3
       start_interval_ms: 1100
+    zai:
+      concurrency: 3
+      start_interval_ms: 1100
     openrouter:
       concurrency: 3
       start_interval_ms: 1100