Remove unused React imports (Notifications, Palette)

Modern React 17+ JSX transform doesn't need `import React from "react"`
unless React itself is referenced. The two component files had stale
imports left over from the agent that scaffolded them; tsc -b under
the build config trips on them as TS6133. Drop them.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/Notifications.tsx

@@ -1,4 +1,3 @@
-import React from "react";
 import "./Notifications.css";
 
 export interface Toast {

src/components/Palette.tsx

@@ -1,4 +1,4 @@
-import React, { useState, useEffect, useRef, useMemo } from "react";
+import { useState, useEffect, useRef, useMemo } from "react";
 import type { LeafNode } from "../lib/layout/tree";
 import "./Palette.css";