feat: gate telemetry behind Cargo feature flags (#8119)

Signed-off-by: Rodolfo Olivieri <rolivier@redhat.com>
Signed-off-by: Douwe Osinga <douwe@squareup.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Co-authored-by: Douwe Osinga <douwe@squareup.com>

crates/goose/src/session/session_manager.rs

@@ -967,6 +967,7 @@ impl SessionStorage {
             .await?;
 
         tx.commit().await?;
+        #[cfg(feature = "telemetry")]
         crate::posthog::emit_session_started();
         Ok(session)
     }