Disposal tweaks (#22999)

The disposal "mainline," the main trunk that wraps around the whole
ship, has been painted with a yellow stripe for better distinction with
both mapping and in-game diagnostics. Relevant code has been changed (a
microscopic amount) to make the stuff actually work, too.

The yellow stuff's currently not constructable due to the colossal
amount of additional codework to make them such for minimal return.

This PR additionally makes packages able to be mailed to the machinist's
workshop properly; due to a mapping error (very easy to miss) people
weren't able to do so before.

(CL)
* Painted the 'mainline' disposal pipes yellow for better distinction
with mapping.
* Adjusted some disposal piping to be tidier.
* Packages can now once again be mailed to the Machinist's Workshop.

## Images
<img width="1274" height="780" alt="image"
src="https://github.com/user-attachments/assets/51374227-f3e7-42ca-8a13-64d278ec0d0b"
/>
<img width="1343" height="1119" alt="image"
src="https://github.com/user-attachments/assets/4ae08fe7-ce09-44a9-8158-99dece757b47"
/>
<img width="1175" height="1092" alt="image"
src="https://github.com/user-attachments/assets/5a1b3aa4-1e51-4bc1-b1f4-2f341cef8ca1"
/>
<img width="449" height="594" alt="image"
src="https://github.com/user-attachments/assets/ba44fb77-8c81-41fc-b07f-a3593e063e41"
/>

code/modules/recycling/disposal.dm

@@ -1084,9 +1084,9 @@
 /obj/structure/disposalpipe/proc/welded()
 	var/obj/structure/disposalconstruct/C = new (src.loc)
 	switch(icon_state)
-		if("pipe-s")
+		if("pipe-s", "pipe-s-yellow", "pipe-s-blue")
 			C.ptype = 0
-		if("pipe-c")
+		if("pipe-c", "pipe-c-yellow", "pipe-c-blue")
 			C.ptype = 1
 		if("pipe-j1")
 			C.ptype = 2
@@ -1135,13 +1135,23 @@
 
 /obj/structure/disposalpipe/segment/Initialize()
 	. = ..()
-	if(icon_state == "pipe-s")
+	if(icon_state == "pipe-s" || icon_state == "pipe-s-yellow" || icon_state == "pipe-s-blue")
 		dpdir = dir | turn(dir, 180)
 	else
 		dpdir = dir | turn(dir, -90)
 
 	update()
 
+/obj/structure/disposalpipe/segment/mainline
+	name = "mainline disposal pipe"
+	desc = "A disposal pipe indicated by a yellow stripe to be part of the main trunk loop."
+	icon_state = "pipe-s-yellow"
+
+/obj/structure/disposalpipe/segment/blue
+	name = "disposal pipe"
+	desc = "A disposal pipe marked by a blue stripe."
+	icon_state = "pipe-s-blue"
+
 /// Z-Level stuff
 /obj/structure/disposalpipe/up
 	icon_state = "pipe-u"

html/changelogs/nauticall-disposaltweaks.yml

@@ -0,0 +1,60 @@
+################################
+# Example Changelog File
+#
+# Note: This file, and files beginning with ".", and files that don't end in ".yml" will not be read. If you change this file, you will look really dumb.
+#
+# Your changelog will be merged with a master changelog. (New stuff added only, and only on the date entry for the day it was merged.)
+# When it is, any changes listed below will disappear.
+#
+# Valid Prefixes:
+#   bugfix
+#     - (fixes bugs)
+#   wip
+#     - (work in progress)
+#   qol
+#     - (quality of life)
+#   soundadd
+#     - (adds a sound)
+#   sounddel
+#     - (removes a sound)
+#   rscadd
+#     - (adds a feature)
+#   rscdel
+#     - (removes a feature)
+#   imageadd
+#     - (adds an image or sprite)
+#   imagedel
+#     - (removes an image or sprite)
+#   spellcheck
+#     - (fixes spelling or grammar)
+#   experiment
+#     - (experimental change)
+#   balance
+#     - (balance changes)
+#   code_imp
+#     - (misc internal code change)
+#   refactor
+#     - (refactors code)
+#   config
+#     - (makes a change to the config files)
+#   admin
+#     - (makes changes to administrator tools)
+#   server
+#     - (miscellaneous changes to server)
+#################################
+
+# Your name.
+author: nauticall
+
+# Optional: Remove this file after generating master changelog.  Useful for PR changelogs that won't get used again.
+delete-after: True
+
+# Any changes you've made.  See valid prefix list above.
+# INDENT WITH TWO SPACES.  NOT TABS.  SPACES.
+# SCREW THIS UP AND IT WON'T WORK.
+# Also, this gets changed to [] after reading.  Just remove the brackets when you add new shit.
+# Please surround your changes in  double quotes ("). It works without them, but if you use certain characters it screws up compiling. The quotes will not show up in the changelog.
+changes:
+  - rscadd: "Painted the 'mainline' disposal pipes yellow for better distinction with mapping."
+  - rscadd: "Adjusted some disposal piping to be tidier."
+  - bugfix: "Packages can now once again be mailed to the Machinist's Workshop."