feat(coding-agent): add InlineExtension type for named inline extension factories (#6267)

* feat(coding-agent): add InlineExtension type for named inline extension factories

* test(coding-agent): update utilities and add regression test for InlineExtension

packages/coding-agent/docs/sdk.md

@@ -604,6 +604,27 @@ const { session } = await createAgentSession({ resourceLoader: loader });
 
 Extensions can register tools, subscribe to events, add commands, and more. See [extensions.md](extensions.md) for the full API.
 
+**Named inline extensions:** By default, inline factories display as `<inline:1>`, `<inline:2>`, etc. in the startup Extensions list. To show a descriptive name instead, wrap the factory:
+
+```typescript
+import type { InlineExtension } from "@earendil-works/pi-coding-agent";
+
+const myProvider: InlineExtension = {
+  name: "my-provider",
+  factory: (pi) => {
+    pi.on("agent_start", () => {
+      console.log("[my-provider] Agent starting");
+    });
+  },
+};
+
+const loader = new DefaultResourceLoader({
+  extensionFactories: [myProvider],
+});
+```
+
+This displays as `<inline:my-provider>` instead of `<inline:1>`. Bare factory functions are still accepted for backward compatibility.
+
 **Event Bus:** Extensions can communicate via `pi.events`. Pass a shared `eventBus` to `DefaultResourceLoader` if you need to emit or listen from outside:
 
 ```typescript
@@ -1161,6 +1182,7 @@ createGrepTool, createFindTool, createLsTool
 type CreateAgentSessionOptions
 type CreateAgentSessionResult
 type ExtensionFactory
+type InlineExtension
 type ExtensionAPI
 type ToolDefinition
 type Skill