fix: log warning when Windows key file permissions fail to set

Replace silently discarded icacls result with proper error handling
that logs a tracing::warn! on failure. Previously, if icacls failed
(binary not found, permission denied), the key file would remain
world-readable on Windows with no indication of the problem.

Closes #56

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/security/secrets.rs

@@ -191,14 +191,26 @@ impl SecretStore {
             #[cfg(windows)]
             {
                 // On Windows, use icacls to restrict permissions to current user only
-                let _ = std::process::Command::new("icacls")
+                match std::process::Command::new("icacls")
                     .arg(&self.key_path)
                     .args(["/inheritance:r", "/grant:r"])
                     .arg(format!(
                         "{}:F",
                         std::env::var("USERNAME").unwrap_or_default()
                     ))
-                    .output();
+                    .output()
+                {
+                    Ok(o) if !o.status.success() => {
+                        tracing::warn!(
+                            "Failed to set key file permissions via icacls (exit code {:?})",
+                            o.status.code()
+                        );
+                    }
+                    Err(e) => {
+                        tracing::warn!("Could not set key file permissions: {e}");
+                    }
+                    _ => {}
+                }
             }
 
             Ok(key)
@@ -241,7 +253,7 @@ fn hex_encode(data: &[u8]) -> String {
 
 /// Hex-decode a hex string to bytes.
 fn hex_decode(hex: &str) -> Result<Vec<u8>> {
-    if hex.len() % 2 != 0 {
+    if !hex.len().is_multiple_of(2) {
         anyhow::bail!("Hex string has odd length");
     }
     (0..hex.len())

src/tools/browser.rs

@@ -366,6 +366,7 @@ impl BrowserTool {
 }
 
 #[async_trait]
+#[allow(clippy::too_many_lines)]
 impl Tool for BrowserTool {
     fn name(&self) -> &str {
         "browser"