Add --stack-path CLI option for custom stack path

Allows overriding the default botserver-stack location via:
- --stack-path /path/to/stack CLI argument
- BOTSERVER_STACK_PATH environment variable

Useful for testing botserver bootstrap in isolated temp directories.

src/core/package_manager/installer.rs

@@ -20,6 +20,8 @@ impl PackageManager {
         let os_type = detect_os();
         let base_path = if mode == InstallMode::Container {
             PathBuf::from("/opt/gbo")
+        } else if let Ok(custom_path) = std::env::var("BOTSERVER_STACK_PATH") {
+            PathBuf::from(custom_path)
         } else {
             std::env::current_dir()?.join("botserver-stack")
         };
@@ -36,6 +38,26 @@ impl PackageManager {
         Ok(pm)
     }
 
+    /// Create a PackageManager with a custom base path (for testing)
+    pub fn with_base_path(
+        mode: InstallMode,
+        tenant: Option<String>,
+        base_path: PathBuf,
+    ) -> Result<Self> {
+        let os_type = detect_os();
+        let tenant = tenant.unwrap_or_else(|| "default".to_string());
+
+        let mut pm = PackageManager {
+            mode,
+            os_type,
+            base_path,
+            tenant,
+            components: HashMap::new(),
+        };
+        pm.register_components();
+        Ok(pm)
+    }
+
     fn register_components(&mut self) {
         self.register_tables();
         self.register_cache();

src/main.rs

@@ -386,6 +386,14 @@ async fn main() -> std::io::Result<()> {
         None
     };
 
+    // Set custom stack path if provided (for testing)
+    if let Some(idx) = args.iter().position(|a| a == "--stack-path") {
+        if let Some(path) = args.get(idx + 1) {
+            std::env::set_var("BOTSERVER_STACK_PATH", path);
+            info!("Using custom stack path: {}", path);
+        }
+    }
+
     // Bootstrap
     trace!("Starting bootstrap process...");
     let progress_tx_clone = progress_tx.clone();