RECONNECTING_PROGRESS_TEXT

The cross-module contract for the WiFi/TCP handshake-watchdog recovery progress signal.

MeshConnectionManager writes this exact literal to connectionProgress immediately before its recovery sibling transitions the transport to ConnectionState.Disconnected, and ConnectionsViewModel (and its tests) compare incoming progress against it to surface RECONNECTING UI state instead of a final-feeling NOT_CONNECTED. The literal text and the U+2026 HORIZONTAL ELLIPSIS character MUST match exactly across both writers and readers — centralizing it here removes the prior cross-module string-contract hazard.