fix: replace unsafe env::set_var with thread-safe OnceLock

Resolves intermittent STATUS_HEAP_CORRUPTION on Windows by using a static OnceLock map instead of mutating the global OS environment block.

server/src/config.rs

@@ -1,43 +1,46 @@
+use std::sync::OnceLock;
 use serde_json::Value;
+use std::collections::HashMap;
 use std::env;
 use std::fs;
 use std::path::PathBuf;
 use tracing::info;
 
+pub static CONFIG_ENV: OnceLock<HashMap<String, String>> = OnceLock::new();
+
 pub fn load_mcp_config_env() {
+    let mut map = HashMap::new();
     let config_path = dirs::home_dir()
         .unwrap_or_else(|| PathBuf::from("."))
         .join(".gemini/config/mcp_config.json");
 
-    if !config_path.exists() {
-        return;
-    }
-
-    let config_str = match fs::read_to_string(&config_path) {
-        Ok(s) => s,
-        Err(_) => return,
-    };
-
-    let parsed: Value = match serde_json::from_str(&config_str) {
-        Ok(v) => v,
-        Err(_) => return,
-    };
-
-    if let Some(env_obj) = parsed
-        .get("mcpServers")
-        .and_then(|v| v.get("mcp-memory"))
-        .and_then(|v| v.get("env"))
-        .and_then(|v| v.as_object())
-    {
-        for (key, val) in env_obj {
-            if let Some(val_str) = val.as_str()
-                && env::var(key).is_err()
-            {
-                unsafe {
-                    env::set_var(key, val_str);
+    if config_path.exists() {
+        if let Ok(config_str) = fs::read_to_string(&config_path) {
+            if let Ok(parsed) = serde_json::from_str::<Value>(&config_str) {
+                if let Some(env_obj) = parsed
+                    .get("mcpServers")
+                    .and_then(|v| v.get("mcp-memory"))
+                    .and_then(|v| v.get("env"))
+                    .and_then(|v| v.as_object())
+                {
+                    for (key, val) in env_obj {
+                        if let Some(val_str) = val.as_str() {
+                            map.insert(key.clone(), val_str.to_string());
+                            info!("Loaded env var {} from mcp_config.json", key);
+                        }
+                    }
                 }
-                info!("Loaded env var {} from mcp_config.json", key);
             }
         }
     }
+    let _ = CONFIG_ENV.set(map);
+}
+
+pub fn get_env(key: &str) -> Result<String, env::VarError> {
+    if let Some(map) = CONFIG_ENV.get() {
+        if let Some(val) = map.get(key) {
+            return Ok(val.clone());
+        }
+    }
+    env::var(key)
 }