feat: add Chrome extension browser relay

assets/chrome-extension/options.js

@@ -0,0 +1,30 @@
+const DEFAULT_PORT = 18792
+
+function clampPort(value) {
+  const n = Number.parseInt(String(value || ''), 10)
+  if (!Number.isFinite(n)) return DEFAULT_PORT
+  if (n <= 0 || n > 65535) return DEFAULT_PORT
+  return n
+}
+
+async function load() {
+  const stored = await chrome.storage.local.get(['relayPort'])
+  const port = clampPort(stored.relayPort)
+  document.getElementById('port').value = String(port)
+}
+
+async function save() {
+  const input = document.getElementById('port')
+  const port = clampPort(input.value)
+  await chrome.storage.local.set({ relayPort: port })
+  input.value = String(port)
+  const status = document.getElementById('status')
+  status.textContent = `Saved. Using http://127.0.0.1:${port}/`
+  setTimeout(() => {
+    status.textContent = ''
+  }, 2000)
+}
+
+document.getElementById('save').addEventListener('click', () => void save())
+void load()
+