Add a decoration glyph for friendly units in tunnels.

mods/ts/rules/defaults.yaml

@@ -625,6 +625,13 @@
 		Categories: Infantry
 	GrantConditionOnTunnelLayer:
 		Condition: inside-tunnel
+	WithDecoration@UNDERGROUND:
+		RequiresCondition: inside-tunnel
+		Position: Center
+		Image: typeglyphs
+		Sequence: infantry
+		Palette: player
+		IsPlayerPalette: true
 
 ^RegularInfantryDeath:
 	WithDeathAnimation@normal:
@@ -820,6 +827,13 @@
 		Categories: Vehicle
 	GrantConditionOnTunnelLayer:
 		Condition: inside-tunnel
+	WithDecoration@UNDERGROUND:
+		RequiresCondition: inside-tunnel
+		Position: Center
+		Image: typeglyphs
+		Sequence: vehicle
+		Palette: player
+		IsPlayerPalette: true
 
 ^Tank:
 	Inherits: ^Vehicle

mods/ts/rules/nod-vehicles.yaml

@@ -439,6 +439,8 @@ SAPC:
 		SubterraneanTransitionSound: subdril1.aud
 	Carryable:
 		RequiresCondition: !submerged
+	WithDecoration@UNDERGROUND:
+		RequiresCondition: inside-tunnel || submerged
 
 SUBTANK:
 	Inherits: ^Tank
@@ -487,6 +489,8 @@ SUBTANK:
 		SubterraneanTransitionSound: subdril1.aud
 	Carryable:
 		RequiresCondition: !submerged
+	WithDecoration@UNDERGROUND:
+		RequiresCondition: inside-tunnel || submerged
 
 STNK:
 	Inherits: ^Tank

mods/ts/rules/shared-vehicles.yaml

@@ -107,6 +107,8 @@ HARV:
 		ResourceSequences:
 			Tiberium: pip-green
 			BlueTiberium: pip-blue
+	WithDecoration@UNDERGROUND:
+		Sequence: harvester
 
 LPST:
 	Inherits: ^Tank