feat: implement ui/notifications/tool-cancelled + add missing App.onteardown (#120)

* feat: implement ui/notifications/tool-cancelled throughout SDK

Wire the tool-cancelled notification that hosts MUST send when tool
execution is cancelled (user action, timeout, classifier intervention, etc.):

- Add McpUiToolCancelledNotification type in spec.types.ts
- Generate Zod schema via ts-to-zod
- Add AppBridge.sendToolCancelled() method for hosts
- Add App.ontoolcancelled setter for guest UIs
- Export type and schema from types.ts
- Add tests for notification with/without reason

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

* feat: add App.onteardown handler for graceful shutdown

Wire the guest UI side of ui/resource-teardown request:

- Add onteardown setter in App class for guest UIs to handle teardown
- Allow ui/resource-teardown in assertRequestHandlerCapability
- Import McpUiResourceTeardownRequest/Result types
- Add tests for sync and async cleanup handlers

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

* feat(example): wire tool-cancelled and teardown in basic-host

Update basic-host example to properly use the new notifications:

- Send sendToolCancelled when tool call promise rejects
- Send sendResourceTeardown when React component unmounts
- Store appBridge ref for cleanup access

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

* fix(example): implement graceful teardown per spec recommendation

Address review feedback: the host now waits for guest's teardown
response before unmounting, following the spec: "Host SHOULD wait
for a response before tearing down the resource (to prevent data loss)."

Changes:
- Add close button to tool call panels
- Two-phase unmount: isDestroying state dims panel and disables events
- sendResourceTeardown() completes before component removal
- Non-app tool results close immediately

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

* feat(examples): add onteardown handlers to demo apps

Demonstrate graceful shutdown with simulated 500ms cleanup work.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

---------

Co-authored-by: Claude <noreply@anthropic.com>

src/generated/schema.json

@@ -1732,6 +1732,28 @@
         }
       ]
     },
+    "McpUiToolCancelledNotification": {
+      "$schema": "https://json-schema.org/draft/2020-12/schema",
+      "type": "object",
+      "properties": {
+        "method": {
+          "type": "string",
+          "const": "ui/notifications/tool-cancelled"
+        },
+        "params": {
+          "type": "object",
+          "properties": {
+            "reason": {
+              "description": "Optional reason for the cancellation (e.g., \"user action\", \"timeout\").",
+              "type": "string"
+            }
+          },
+          "additionalProperties": false
+        }
+      },
+      "required": ["method", "params"],
+      "additionalProperties": false
+    },
     "McpUiToolInputNotification": {
       "$schema": "https://json-schema.org/draft/2020-12/schema",
       "type": "object",

src/generated/schema.test.ts

@@ -51,6 +51,10 @@ export type McpUiToolInputPartialNotificationSchemaInferredType = z.infer<
   typeof generated.McpUiToolInputPartialNotificationSchema
 >;
 
+export type McpUiToolCancelledNotificationSchemaInferredType = z.infer<
+  typeof generated.McpUiToolCancelledNotificationSchema
+>;
+
 export type McpUiResourceTeardownRequestSchemaInferredType = z.infer<
   typeof generated.McpUiResourceTeardownRequestSchema
 >;
@@ -151,6 +155,12 @@ expectType<spec.McpUiToolInputPartialNotification>(
 expectType<McpUiToolInputPartialNotificationSchemaInferredType>(
   {} as spec.McpUiToolInputPartialNotification,
 );
+expectType<spec.McpUiToolCancelledNotification>(
+  {} as McpUiToolCancelledNotificationSchemaInferredType,
+);
+expectType<McpUiToolCancelledNotificationSchemaInferredType>(
+  {} as spec.McpUiToolCancelledNotification,
+);
 expectType<spec.McpUiResourceTeardownRequest>(
   {} as McpUiResourceTeardownRequestSchemaInferredType,
 );

src/generated/schema.ts

@@ -160,6 +160,24 @@ export const McpUiToolInputPartialNotificationSchema = z.object({
   }),
 });
 
+/**
+ * @description Notification that tool execution was cancelled (Host -> Guest UI).
+ * Host MUST send this if tool execution was cancelled for any reason (user action,
+ * sampling error, classifier intervention, etc.).
+ */
+export const McpUiToolCancelledNotificationSchema = z.object({
+  method: z.literal("ui/notifications/tool-cancelled"),
+  params: z.object({
+    /** @description Optional reason for the cancellation (e.g., "user action", "timeout"). */
+    reason: z
+      .string()
+      .optional()
+      .describe(
+        'Optional reason for the cancellation (e.g., "user action", "timeout").',
+      ),
+  }),
+});
+
 /**
  * @description Request for graceful shutdown of the Guest UI (Host -> Guest UI).
  * @see {@link app-bridge.AppBridge.sendResourceTeardown} for the host method that sends this