fix(startup): enforce consent before download handoffs

Gate clipboard, extension, and deep-link inputs until startup consent is resolved, and serialize extension readiness transitions so native prompts cannot race the app explanation. Identify consent by the build revision so same-version updates re-enter the consent boundary.

Requested by [this X post](https://x.com/ixabolfazl/status/2077356127763804450?s=20).

vite.config.ts

@@ -1,13 +1,32 @@
 import { defineConfig } from "vitest/config";
+import { execFileSync } from "node:child_process";
 import react from "@vitejs/plugin-react";
 import tailwindcss from '@tailwindcss/vite';
 
 // @ts-expect-error process is a nodejs global
 const host = process.env.TAURI_DEV_HOST;
 
+const buildId = (() => {
+  // Release-candidate builds can keep the same semantic app version. The
+  // source revision is the stable identity needed for consent migrations.
+  const configured = process.env.VITE_BUILD_ID?.trim();
+  if (configured) return configured;
+  try {
+    return execFileSync('git', ['rev-parse', 'HEAD'], {
+      encoding: 'utf8',
+      stdio: ['ignore', 'pipe', 'ignore']
+    }).trim() || 'unknown';
+  } catch {
+    return 'unknown';
+  }
+})();
+
 // https://vite.dev/config/
 export default defineConfig(async () => ({
   plugins: [react(), tailwindcss()],
+  define: {
+    'import.meta.env.VITE_BUILD_ID': JSON.stringify(buildId)
+  },
   test: {
     exclude: [
       "Extensions/**",