style(sidecar): apply rustfmt

Format the sidecar source with `cargo fmt` so the new `cargo fmt --check`
CI gate passes on the first run. No behavior change.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0114TpmrNW4wNXsHq5CR72jQ

sidecar/src/config.rs

@@ -142,7 +142,10 @@ fn persist_token(path: &str, token: &str) -> anyhow::Result<()> {
     let text = fs::read_to_string(path)?;
     let line = format!("auth_token = \"{token}\"");
 
-    if text.lines().any(|l| l.trim_start().starts_with("auth_token")) {
+    if text
+        .lines()
+        .any(|l| l.trim_start().starts_with("auth_token"))
+    {
         let out: String = text
             .lines()
             .map(|l| {