fix: prevent keyboard freeze when MCP notification effects fire

React 19 requires `supportsMicrotasks: true` in the reconciler host
config so it can flush state updates from passive effects via
queueMicrotask. Without this, state updates triggered inside
useMcpConnectivityStatus were silently dropped, corrupting React's
internal executionContext and causing all keyboard input to freeze
after the "N MCP server(s) need auth" notification appeared.

Root cause (three-part fix):

1. reconciler.ts: declare supportsMicrotasks + scheduleMicrotask so
   React 19 schedules passive-effect flushes correctly.

2. useMcpConnectivityStatus.tsx: wrap the MCP auth notification effect
   in try/catch so any unexpected throw does not propagate into
   flushPassiveEffects and permanently corrupt executionContext.

3. notifications.tsx: wrap addNotification, removeNotification, and
   processQueue in try/catch for the same reason — these are called
   from 12+ notification hooks across passive effects.

Also fixes a pre-existing test isolation bug in context.test.ts where
assigning `undefined` to process.env produced the string "undefined",
polluting the env for subsequent test files.

Resolves: #169, #205, #77

src/context/notifications.tsx

@@ -1,6 +1,7 @@
 import type * as React from 'react';
 import { useCallback, useEffect } from 'react';
 import { useAppStateStore, useSetAppState } from 'src/state/AppState.js';
+import { logError } from '../utils/log.js';
 import type { Theme } from '../utils/theme.js';
 type Priority = 'low' | 'medium' | 'high' | 'immediate';
 type BaseNotification = {
@@ -44,6 +45,7 @@ export function useNotifications(): {
 
   // Process queue when current notification finishes or queue changes
   const processQueue = useCallback(() => {
+    try {
     setAppState(prev => {
       const next = getNext(prev.notifications.queue);
       if (prev.notifications.current !== null || !next) {
@@ -74,8 +76,12 @@ export function useNotifications(): {
         }
       };
     });
+    } catch (error) {
+      logError(error);
+    }
   }, [setAppState]);
   const addNotification = useCallback<AddNotificationFn>((notif: Notification) => {
+    try {
     // Handle immediate priority notifications
     if (notif.priority === 'immediate') {
       // Clear any existing timeout since we're showing a new immediate notification
@@ -189,8 +195,12 @@ export function useNotifications(): {
 
     // Process queue after adding the notification
     processQueue();
+    } catch (error) {
+      logError(error);
+    }
   }, [setAppState, processQueue]);
   const removeNotification = useCallback<RemoveNotificationFn>((key: string) => {
+    try {
     setAppState(prev => {
       const isCurrent = prev.notifications.current?.key === key;
       const inQueue = prev.notifications.queue.some(n => n.key === key);
@@ -210,6 +220,9 @@ export function useNotifications(): {
       };
     });
     processQueue();
+    } catch (error) {
+      logError(error);
+    }
   }, [setAppState, processQueue]);
 
   // Process queue on mount if there are notifications in the initial state.