Fix: Water cooler reagents are now visible to observers and scientists (#95636) (#96335)

## About The Pull Request

This PR adds a `can_see_reagents()` check to the `examine()` function of
the water cooler (`/obj/structure/reagent_dispensers/water_cooler`).
It loops through the reagents and prints their specific volume and name,
mirroring the behavior of standard transparent containers when examined
by an authorized user.

Fixes #95636

## Why It's Good For The Game

The current state of the water cooler is inconsistent with other reagent
containers. As reported in the original issue, observers cannot see what
custom reagents are inside.

Furthermore, during local testing, I verified that this also negatively
impacts active gameplay, Chemists and Scientists wearing Science Goggles
are unable to read the chemical breakdown of the cooler's contents,
breaking immersion.

This PR implements the standard check without altering the cooler's
opaque identity for regular players.

**Before:**
<img width="2559" height="1391" alt="Screenshot 2026-06-03 155849"
src="https://github.com/user-attachments/assets/8b74fca7-5fe8-4a08-af23-9a1d4b5a5647"
/>
<img width="819" height="717" alt="Screenshot 2026-06-03 155929"
src="https://github.com/user-attachments/assets/21150f27-9806-4a6a-90b0-2ec4129b5492"
/>

**After:**
<img width="2559" height="1393" alt="Screenshot 2026-06-03 163407"
src="https://github.com/user-attachments/assets/84b368c7-46e6-4134-9ccb-65956fa5d58f"
/>
<img width="2559" height="1390" alt="Screenshot 2026-06-03 163422"
src="https://github.com/user-attachments/assets/7b13070f-193b-467f-9166-a00fdf8ea65e"
/>

## Changelog
🆑
fix: Water coolers now properly reveal their custom reagents when
examined by ghosts or players with science goggles.
/🆑

code/modules/reagents/reagent_dispenser.dm

@@ -35,6 +35,8 @@
 	var/last_rigger = ""
 	/// is it climbable? some of our wall-mounted dispensers should not have this
 	var/climbable = FALSE
+	/// Flags passed to the reagents datum upon creation
+	var/reagent_flags = DRAINABLE | AMOUNT_VISIBLE
 
 // This check is necessary for assemblies to automatically detect that we are compatible
 /obj/structure/reagent_dispensers/IsSpecialAssembly()
@@ -152,7 +154,7 @@
 	UnregisterSignal(src, COMSIG_IGNITER_ACTIVATE)
 
 /obj/structure/reagent_dispensers/Initialize(mapload)
-	create_reagents(tank_volume, DRAINABLE | AMOUNT_VISIBLE)
+	create_reagents(tank_volume, reagent_flags)
 	if(reagent_id)
 		reagents.add_reagent(reagent_id, tank_volume)
 	. = ..()
@@ -358,6 +360,7 @@ MAPPING_DIRECTIONAL_HELPERS(/obj/structure/reagent_dispensers/wall/peppertank, 3
 	desc = "A machine that cools and dispenses liquids to drink. The 'hot' handle doesn't seem to do anything."
 	icon_state = "water_cooler"
 	anchored = TRUE
+	reagent_flags = DRAINABLE | TRANSPARENT
 	tank_volume = 200
 	can_be_tanked = FALSE
 	max_integrity = 150