Bug-fix pass for reported issues #114-#119 (D424-D434)

Recoil byte order, crouch-tank interactions, auto-fire cadence in ticks,
hipfire turret tracking, light-fixture Gfx index parsing, hit-type byte
reads. Rule-2 sign-offs recorded for D424 and D427. Documentation re-triaged
onto a single tracker (docs/ROADMAP.md).

Refs: D424 D425 D426 D427 D428 D430 D431 D432 D434 #114 #115 #116 #117 #118 #119

src/game/propobj.c

@@ -9682,7 +9682,12 @@ void objHit(ShotData *shotdata, BulletHit *hit)
             }
             else
             {
+#ifdef PORT
+                /* D434: raw byte 0 of the PORT image_entry is dataoffset's low byte, not the hit type. */
+                impact_sounds = g_HitTypeSounds[g_Textures[texturenum].hitTexture];
+#else
                 impact_sounds = g_HitTypeSounds[((u8 *)&g_Textures[texturenum])[0] & 0x0f];
+#endif
             }
 
             thing2_index = randomGetNext() % impact_sounds->thing2_len;