feat: expand secure assistant workflows

Harden runtime execution and add local knowledge, Smart Heartbeat, usage visibility, responsive product surfaces, and cross-platform packaging support.

Co-authored-by: factory-droid[bot] <138933559+factory-droid[bot]@users.noreply.github.com>

src/preload/preload-sandbox.test.ts

@@ -0,0 +1,14 @@
+import { readFileSync } from 'node:fs'
+import { join } from 'node:path'
+import { describe, expect, it } from 'vitest'
+
+describe('sandboxed preload', () => {
+  it('does not import Node built-ins unavailable in Electron sandbox', () => {
+    const source = readFileSync(
+      join(process.cwd(), 'src', 'preload', 'index.ts'),
+      'utf8'
+    )
+    expect(source).not.toMatch(/\bfrom\s+['"]node:/u)
+    expect(source).not.toMatch(/\brequire\(\s*['"]node:/u)
+  })
+})