feat: add Config::init_global(path) to support custom config directories

Add Config::init_global(config_dir) that initializes the global singleton
with a caller-provided config directory instead of the default. This
addresses PR feedback that Config::global() silently ignored the
config_dir field from AcpServerFactoryConfig.

The server factory now calls init_global(config_dir) so that if a
non-default config directory is ever passed, the global Config will
use the correct path while still providing the singleton mutex
serialization benefit.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: matt2e

crates/goose/src/acp/server_factory.rs

@@ -21,7 +21,7 @@ impl AcpServer {
     }
 
     pub async fn create_agent(&self) -> Result<Arc<GooseAcpAgent>> {
-        let config = crate::config::Config::global();
+        let config = crate::config::Config::init_global(self.config.config_dir.clone());
 
         let goose_mode = config
             .get_goose_mode()

crates/goose/src/config/base.rs

@@ -265,6 +265,38 @@ impl Config {
         GLOBAL_CONFIG.get_or_init(Config::default)
     }
 
+    /// Initialize the global configuration with a custom config directory.
+    ///
+    /// If the global instance has already been initialized (e.g. by a prior call
+    /// to `global()` or `init_global()`), this returns the existing instance and
+    /// the provided path is ignored. This is safe because Goose runs one ACP
+    /// server per process.
+    pub fn init_global(config_dir: PathBuf) -> &'static Config {
+        GLOBAL_CONFIG.get_or_init(|| {
+            let config_path = config_dir.join(CONFIG_YAML_NAME);
+
+            let secrets =
+                if env::var("GOOSE_DISABLE_KEYRING").is_ok()
+                    || keyring_disabled_in_config(&config_path)
+                {
+                    SecretStorage::File {
+                        path: config_dir.join("secrets.yaml"),
+                    }
+                } else {
+                    SecretStorage::Keyring {
+                        service: KEYRING_SERVICE.to_string(),
+                    }
+                };
+
+            Config {
+                config_path,
+                secrets,
+                guard: Mutex::new(()),
+                secrets_cache: Arc::new(Mutex::new(None)),
+            }
+        })
+    }
+
     /// Create a new configuration instance with custom paths
     ///
     /// This is primarily useful for testing or for applications that need