Rename movement/world methods to idiomatic Go; remove all gotos

Refactor step 4. Renames (C breadcrumbs kept in doc comments):
doMove→moveHero, beTrapped→springTrap, rndmove→randomStep,
doRooms→digRooms, doPassages→digPassages, doMaze→digMaze,
chgStr→changeStrength, doRun→startRun, moveStuff→finishMove,
turnref→turnRefresh, moveMonst→moveMonster, doChase→chaseStep,
setOldch→setOldChar, cansee→canSee, roomin→roomIn, runto→runTo,
conn→connectRooms, putpass→putPassage, passnum→numberPassages,
numpass→numberPassage, rndPos→randomPos, rndRoom→randomRoom,
treasRoom→treasureRoom, accntMaze→accountMaze.

All goto/label flows are gone: moveHero uses a retry loop with the
PASSGO corner logic extracted into passageTurn; dispatch re-dispatches
via a loop; chaseStep re-checks via a loop; saveGame uses a labeled
prompt loop. Control flow and RNG call order are unchanged; suite
green.

game/potions.go

@@ -49,7 +49,7 @@ func (g *RogueGame) quaff() {
 		if p.IsWearing(RingSustainStrength) {
 			g.msg("you feel momentarily sick")
 		} else {
-			g.chgStr(-(g.rnd(3) + 1))
+			g.changeStrength(-(g.rnd(3) + 1))
 			g.msg("you feel very sick now")
 			g.comeDown(0)
 		}
@@ -64,7 +64,7 @@ func (g *RogueGame) quaff() {
 		g.msg("you begin to feel better")
 	case PotionGainStrength:
 		g.Items.Potions[PotionGainStrength].Know = true
-		g.chgStr(1)
+		g.changeStrength(1)
 		g.msg("you feel stronger, now.  What bulging muscles!")
 	case PotionDetectMonsters:
 		p.Flags.Set(SenseMonsters)