fix(agents): make image sanitization dimension configurable

docs/gateway/configuration.md

@@ -126,6 +126,7 @@ When validation fails:
 
     - `agents.defaults.models` defines the model catalog and acts as the allowlist for `/model`.
     - Model refs use `provider/model` format (e.g. `anthropic/claude-opus-4-6`).
+    - `agents.defaults.imageMaxDimensionPx` controls transcript/tool image downscaling (default `1200`).
     - See [Models CLI](/concepts/models) for switching models in chat and [Model Failover](/concepts/model-failover) for auth rotation and fallback behavior.
     - For custom/self-hosted providers, see [Custom providers](/gateway/configuration-reference#custom-providers-and-base-urls) in the reference.
 

docs/reference/transcript-hygiene.md

@@ -57,6 +57,7 @@ Implementation:
 
 - `sanitizeSessionMessagesImages` in `src/agents/pi-embedded-helpers/images.ts`
 - `sanitizeContentBlocksImages` in `src/agents/tool-images.ts`
+- Max image side is configurable via `agents.defaults.imageMaxDimensionPx` (default: `1200`).
 
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