Bump protocol version to 3 and guard fallback RPC calls

- Bump SDK_PROTOCOL_VERSION from 2 to 3 to match runtime breaking change
- Wrap fallback RPC calls in _executeToolAndRespond and
  _executePermissionAndRespond with try/catch to prevent unhandled
  rejections if the connection is disposed mid-flight

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

Author: SteveSandersonMS

nodejs/src/sdkProtocolVersion.ts

@@ -8,7 +8,7 @@
  * The SDK protocol version.
  * This must match the version expected by the copilot-agent-runtime server.
  */
-export const SDK_PROTOCOL_VERSION = 2;
+export const SDK_PROTOCOL_VERSION = 3;
 
 /**
  * Gets the SDK protocol version.

nodejs/src/session.ts

@@ -370,7 +370,11 @@ export class CopilotSession {
         } catch (error) {
             const message =
                 error instanceof Error ? error.message : String(error);
-            await this.rpc.tools.handlePendingToolCall({ requestId, error: message });
+            try {
+                await this.rpc.tools.handlePendingToolCall({ requestId, error: message });
+            } catch {
+                // Connection may have been disposed; nothing more we can do.
+            }
         }
     }
 
@@ -388,12 +392,16 @@ export class CopilotSession {
             });
             await this.rpc.permissions.handlePendingPermissionRequest({ requestId, result });
         } catch (_error) {
-            await this.rpc.permissions.handlePendingPermissionRequest({
-                requestId,
-                result: {
-                    kind: "denied-no-approval-rule-and-could-not-request-from-user",
-                },
-            });
+            try {
+                await this.rpc.permissions.handlePendingPermissionRequest({
+                    requestId,
+                    result: {
+                        kind: "denied-no-approval-rule-and-could-not-request-from-user",
+                    },
+                });
+            } catch {
+                // Connection may have been disposed; nothing more we can do.
+            }
         }
     }