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/things.go

@@ -201,7 +201,7 @@ func (g *RogueGame) dropCheck(obj *Object) bool {
 
 		switch obj.RingKind() {
 		case RingAddStrength:
-			g.chgStr(-obj.Bonus)
+			g.changeStrength(-obj.Bonus)
 		case RingSeeInvisible:
 			g.unsee(0)
 			g.Extinguish(DUnsee)