Document model_providers headers in configuration reference

Co-authored-by: Musa <musa@spherrrical.dev>

docs/source/resources/includes/plano_config_full_reference.yaml

@@ -47,6 +47,14 @@ model_providers:
     http_host: api.custom-provider.com
     access_key: $CUSTOM_API_KEY
 
+  # headers: optional map of extra HTTP headers sent on upstream requests (after auth).
+  # Use for provider-specific requirements such as User-Agent, org IDs, or account headers.
+  - model: moonshotai/kimi-for-coding
+    access_key: $MOONSHOTAI_API_KEY
+    base_url: https://api.kimi.com/coding/v1
+    headers:
+      User-Agent: "KimiCLI/1.3"
+
 # Model aliases - use friendly names instead of full provider model names
 model_aliases:
   fast-llm:

docs/source/resources/includes/plano_config_full_reference_rendered.yaml

@@ -88,6 +88,18 @@ listeners:
     port: 443
     protocol: https
     provider_interface: openai
+  - access_key: $MOONSHOTAI_API_KEY
+    base_url: https://api.kimi.com/coding/v1
+    base_url_path_prefix: /coding/v1
+    cluster_name: moonshotai_api.kimi.com
+    endpoint: api.kimi.com
+    headers:
+      User-Agent: KimiCLI/1.3
+    model: kimi-for-coding
+    name: moonshotai/kimi-for-coding
+    port: 443
+    protocol: https
+    provider_interface: moonshotai
   name: model_1
   output_filters:
   - input_guards
@@ -144,6 +156,18 @@ model_providers:
   port: 443
   protocol: https
   provider_interface: openai
+- access_key: $MOONSHOTAI_API_KEY
+  base_url: https://api.kimi.com/coding/v1
+  base_url_path_prefix: /coding/v1
+  cluster_name: moonshotai_api.kimi.com
+  endpoint: api.kimi.com
+  headers:
+    User-Agent: KimiCLI/1.3
+  model: kimi-for-coding
+  name: moonshotai/kimi-for-coding
+  port: 443
+  protocol: https
+  provider_interface: moonshotai
 - internal: true
   model: Plano-Orchestrator
   name: plano-orchestrator