fix(HealthColors): enhance integration with improved reliability and diagnostics

Address compatibility issues with Beacon/D&D 2024 sheets by introducing alias-aware attribute resolution and preferring the `getSheetItem` API for live value reads. Prevent sandbox errors from unknown sheet fields by caching their status and suppressing repeated probes. Add a polling mechanism to ensure death-save markers update on sheets that do not emit `change:attribute` events. Provide GMs with new `sync` command to force updates for selected tokens and an enhanced `debug` command for better diagnostics. Implement a one-time GM warning for Beacon sheets regarding the Experimental (Jumpgate) sandbox requirement for live syncing.

Signed-off-by: Steve Roberts <steve@shadowcomputers.co.uk>