feat: add deepseek-agents extension (auto-injects deepseek model)

extensions/deepseek-agents.ts

@@ -0,0 +1,31 @@
+// ABOUTME: DeepSeek Agent Default — auto-injects deepseek-v4-flash model into subagent_create calls
+// ABOUTME: Intercepts tool_call events and patches the model parameter when not explicitly set
+
+import type { ExtensionAPI, ExtensionContext, ToolCallEvent, ToolCallEventResult } from "@mariozechner/pi-coding-agent";
+
+export default function (pi: ExtensionAPI) {
+  pi.on("tool_call", (event: ToolCallEvent, _ctx: ExtensionContext): ToolCallEventResult | void => {
+    // Only intercept subagent_create calls
+    if (event.toolName === "subagent_create") {
+      const input = event.input as Record<string, unknown>;
+      
+      // Only inject model if not explicitly set by the user
+      if (!input.model) {
+        input.model = "deepseek-v4-flash";
+      }
+    }
+    
+    // Also intercept subagent_create_batch to inject model into each agent
+    if (event.toolName === "subagent_create_batch") {
+      const input = event.input as Record<string, unknown>;
+      const agents = input.agents as Array<Record<string, unknown>> | undefined;
+      if (agents) {
+        for (const agent of agents) {
+          if (!agent.model) {
+            agent.model = "deepseek-v4-flash";
+          }
+        }
+      }
+    }
+  });
+}