feat: enhance error handling in OAuth URL building and client creation; improve tool argument sanitization

src/model/app_config.rs

@@ -60,10 +60,19 @@ impl AppConfig {
     pub fn load() -> Self {
         let store = super::store::Store::new();
         let path = store.base_dir.join("app_config.json");
-        let mut cfg: AppConfig = std::fs::read_to_string(path)
-            .ok()
-            .and_then(|s| serde_json::from_str(&s).ok())
-            .unwrap_or_default();
+        let mut cfg: AppConfig = match std::fs::read_to_string(&path) {
+            Ok(s) => match serde_json::from_str(&s) {
+                Ok(c) => c,
+                Err(e) => {
+                    eprintln!(
+                        "warning: failed to parse config file '{}': {}. Loading defaults.",
+                        path.display(), e
+                    );
+                    Self::default()
+                }
+            },
+            Err(_) => Self::default(),
+        };
         // Merge any default providers not present in the loaded config
         let defaults = Self::default();
         for (name, provider) in defaults.providers {

src/model/session_lock.rs

@@ -32,6 +32,9 @@ impl SessionLock {
     }
 
     fn is_alive(&self, pid: u32) -> bool {
+        // SAFETY: `libc::kill(pid, 0)` does not send a signal; it only checks
+        // whether the process exists and the caller has permission to signal
+        // it. The integer argument is a PID already validated by `try_lock`.
         unsafe { libc::kill(pid as i32, 0) == 0 }
     }
 }