fix: correct Python permission handler in steering guide

Fix all 3 Python snippets to use the correct signature:
- 2-arg lambda (req, inv) matching PermissionHandlerFn typedef
- Return PermissionRequestResult dataclass instead of plain dict
- Add 'from copilot.types import PermissionRequestResult' import

The previous pattern (lambda req: {"kind": "approved"}) would fail
at runtime: TypeError from wrong arg count, and AttributeError from
dict lacking .kind attribute access.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: patniko

docs/guides/steering-and-queueing.md

@@ -70,14 +70,15 @@ await session.send({
 
 ```python
 from copilot import CopilotClient
+from copilot.types import PermissionRequestResult
 
 async def main():
     client = CopilotClient()
     await client.start()
 
     session = await client.create_session({
         "model": "gpt-4.1",
-        "on_permission_request": lambda req: {"kind": "approved"},
+        "on_permission_request": lambda req, inv: PermissionRequestResult(kind="approved"),
     })
 
     # Start a long-running task
@@ -228,14 +229,15 @@ await session.send({
 
 ```python
 from copilot import CopilotClient
+from copilot.types import PermissionRequestResult
 
 async def main():
     client = CopilotClient()
     await client.start()
 
     session = await client.create_session({
         "model": "gpt-4.1",
-        "on_permission_request": lambda req: {"kind": "approved"},
+        "on_permission_request": lambda req, inv: PermissionRequestResult(kind="approved"),
     })
 
     # Send an initial task
@@ -358,7 +360,7 @@ await session.send({
 ```python
 session = await client.create_session({
     "model": "gpt-4.1",
-    "on_permission_request": lambda req: {"kind": "approved"},
+    "on_permission_request": lambda req, inv: PermissionRequestResult(kind="approved"),
 })
 
 # Start a task