fix(gui): 缓存解封结果，否则每个请求都要 spawn 一个进程

The auth rule calls readAdminKey() on every outbound request so injection
never depends on ordering. Once the sealed-config path shells out to the
core, that turns each request into a process spawn: 200 simulated requests
took 1012ms and launched 200 cores.

Cache the unsealed key against config.yaml's mtime. Editing the config still
invalidates it, which is what the auth rule actually needs -- the port
rewrite, the first write, and a user edit all change mtime. Measured: 200
requests now cost 10ms and one spawn.

Only a successful unseal is cached. Caching a failure would pin an empty key
until the config next changes, turning a momentary spawn error into a locked
out user.

cmd/gui/main.js

@@ -142,7 +142,17 @@ function readConfigRaw() {
 // the core generate a *second* master key in the CWD and then fail to decrypt
 // ("master key changed?"). Electron's CWD is not the profile dir, so this is
 // not optional: without it the desktop build cannot read its own key back.
+//
+// readAdminKey runs on every outbound request, and this spawns a process, so
+// the result is cached against the config's mtime. Editing the config (or the
+// port rewrite, or the first write) changes the mtime and invalidates it, which
+// keeps the "read live so ordering never matters" property the auth rule
+// depends on.
 function unsealViaCore() {
+  const st = safeStat(CONFIG_FILE);
+  const stamp = st ? st.mtimeMs : 0;
+  if (unsealCache && unsealCache.stamp === stamp) return unsealCache.key;
+  let key = "";
   try {
     const out = execFileSync(
       CORE_EXE,
@@ -157,14 +167,29 @@ function unsealViaCore() {
     // -show-secrets prints one line per credential:
     //   key    <name>  role=<role>  <value>
     const admin = /^key\s+\S+\s+role=admin\s+(\S+)\s*$/m.exec(out);
-    if (admin && admin[1]) return admin[1];
+    if (admin && admin[1]) key = admin[1];
     // Tolerate a field-order or spacing change rather than locking the user out.
-    const loose = /role=admin\s+(\S+)/.exec(out);
-    if (loose && loose[1]) return loose[1];
+    if (!key) {
+      const loose = /role=admin\s+(\S+)/.exec(out);
+      if (loose && loose[1]) key = loose[1];
+    }
   } catch (e) {
     console.error("unseal via core failed:", e.message);
   }
-  return "";
+  // Only cache a success. A transient failure must not pin an empty key until
+  // the config next changes, or a momentary spawn error locks the user out.
+  if (key) unsealCache = { stamp, key };
+  return key;
+}
+
+let unsealCache = null;
+
+function safeStat(p) {
+  try {
+    return fs.statSync(p);
+  } catch (e) {
+    return null;
+  }
 }
 
 const embeddedBaseUrl = () =>