docs: add steering and queueing guide (#714)

* docs: add steering and queueing guide

Add a comprehensive guide covering the two message delivery modes
available through the SDK:

- Steering (immediate mode): inject messages into the current agent
  turn for real-time course correction
- Queueing (enqueue mode): buffer messages for sequential processing
  after the current turn completes

Includes code examples for all four SDK languages (Node.js, Python,
Go, .NET), a sequence diagram, API reference, UI building patterns,
and best practices.

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

* 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>

* fix: correct Python permission handler in skills and custom-agents guides

Same fix as the steering guide — use correct 2-arg signature and
PermissionRequestResult dataclass return type.

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

---------

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

Author: patniko

docs/guides/custom-agents.md

@@ -65,6 +65,7 @@ const session = await client.createSession({
 
 ```python
 from copilot import CopilotClient
+from copilot.types import PermissionRequestResult
 
 client = CopilotClient()
 await client.start()
@@ -87,7 +88,7 @@ session = await client.create_session({
             "prompt": "You are a code editor. Make minimal, surgical changes to files as requested.",
         },
     ],
-    "on_permission_request": lambda req: {"kind": "approved"},
+    "on_permission_request": lambda req, inv: PermissionRequestResult(kind="approved"),
 })
 ```
 

docs/guides/skills.md

@@ -43,6 +43,7 @@ await session.sendAndWait({ prompt: "Review this code for security issues" });
 
 ```python
 from copilot import CopilotClient
+from copilot.types import PermissionRequestResult
 
 async def main():
     client = CopilotClient()
@@ -54,7 +55,7 @@ async def main():
             "./skills/code-review",
             "./skills/documentation",
         ],
-        "on_permission_request": lambda req: {"kind": "approved"},
+        "on_permission_request": lambda req, inv: PermissionRequestResult(kind="approved"),
     })
 
     # Copilot now has access to skills in those directories