Fix review findings and Windows setup issues found in testing

- Run the server with -X utf8: the bundled Windows Python ignores PYTHON* variables.
- Quote every argument in Windows terminal commands, so cmd metacharacters are literal.
- frame_connect: accept HOST:PORT, validate input, retry the config swap while
  Windows' ssh.exe holds ~/.ssh/config locked, and don't apply 0o700 on Windows.
- Never use rsync on Windows; unbounded stream queue; validate FRAME_ALIAS;
  more Linux terminals; bundle the window icon; docs and wording fixes.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

app/main.js

@@ -109,7 +109,7 @@ function ping(target) {
 
 async function startServer() {
   const env = { ...process.env, PATH: await loginPath(), PYTHONUNBUFFERED: "1", PYTHONDONTWRITEBYTECODE: "1",
-                PYTHONIOENCODING: "utf-8", PYTHONUTF8: "1", FRAME_CONTROL_APP: "1" };  // UTF-8 even on Windows
+                PYTHONIOENCODING: "utf-8", PYTHONUTF8: "1", FRAME_CONTROL_APP: "1" };
   python = await findPython(env);
   if (!python) throw new Error(`Frame Control needs Python 3.8 or later. ${PYTHON_HELP}`);
   if (!await hasSsh(env)) throw new Error(`Frame Control needs the ssh command. ${SSH_HELP}`);
@@ -118,7 +118,8 @@ async function startServer() {
   const log = fs.openSync(LOG, "a");
   fs.writeSync(log, `\n--- ${new Date().toISOString()} ${python} ${SERVER} --port ${port}\n`);
   // stdin stays open while the app runs; the server exits cleanly when it closes.
-  const child = spawn(python, [SERVER, "--port", String(port), "--exit-on-eof"],
+  // -X utf8: the bundled Windows Python ignores PYTHON* variables (isolated mode).
+  const child = spawn(python, ["-X", "utf8", SERVER, "--port", String(port), "--exit-on-eof"],
                       { env, stdio: ["pipe", log, log], windowsHide: true });
   child.stdin.on("error", () => {});
   fs.closeSync(log);