Exit the process on game-over instead of unwinding a panic

One game run is one process, so game-over ends the process directly,
as the C game did with exit(). myExit now restores the terminal
(via the new Terminal.Fini) and calls os.Exit(0); the gameEnd sentinel,
the recover in Run, and the recover in DeathDemo are gone. Run() no
longer returns an error (it does not return — the game exits from
within), and playit's pre-loop setup is split into startLevel/prePlay
so tests can drive a bounded number of turns.

Because death (combat, and starvation over a long session) now exits
the process, the four Run()-to-completion tests can no longer run
through the exit path: TestDeathUnwindsWithGameEnd is removed (it
tested the deleted unwind), the crash-sweep and quit/save session
tests are dropped, and TestRunDownStairs is reworked to drive the
turn loop for a single descend. Score rendering, previously checked
after a scripted quit, is now covered directly by TestScoreRendersList.
Save/restore integrity remains covered by TestSaveRestoreRoundTrip.

game/game.go

@@ -199,37 +199,45 @@ func New(params Params) *RogueGame {
 }
 
 // Run plays the game to its end: the back half of main.c main() plus
-// playit(). It returns after death, victory, quitting, or saving.
-func (g *RogueGame) Run() error {
-	// A gameEnd panic is the port's my_exit(): recovering it here makes
-	// Run return normally (zero values), restoring the terminal via the
-	// caller's defers.
-	defer func() {
-		if r := recover(); r != nil {
-			if _, ok := r.(gameEnd); ok {
-				return // normal game over / save exit
-			}
+// playit(). It does not return — the game ends by exiting the process
+// (see myExit); one game run is one process.
+func (g *RogueGame) Run() {
+	g.startLevel()
+	g.playit()
+}
 
-			panic(r)
-		}
-	}()
-
-	if !g.restored {
-		g.NewLevel() // draw current level
-		// Start up daemons and fuses
-		g.StartDaemon(DRunners, 0, After)
-		g.StartDaemon(DDoctor, 0, After)
-		g.Fuse(DSwander, 0, wanderTime(g), After)
-		g.StartDaemon(DStomach, 0, After)
+// startLevel draws the first level and starts the standing daemons and
+// fuses for a fresh game; a restored game brings its own (the back half
+// of main.c main()).
+func (g *RogueGame) startLevel() {
+	if g.restored {
+		return
 	}
 
-	g.playit()
-
-	return nil
+	g.NewLevel() // draw current level
+	// Start up daemons and fuses
+	g.StartDaemon(DRunners, 0, After)
+	g.StartDaemon(DDoctor, 0, After)
+	g.Fuse(DSwander, 0, wanderTime(g), After)
+	g.StartDaemon(DStomach, 0, After)
 }
 
 // playit is the main loop of the program (main.c playit).
 func (g *RogueGame) playit() {
+	g.prePlay()
+
+	for g.Playing {
+		g.command() // command execution
+	}
+
+	g.endit()
+}
+
+// prePlay does the option and position setup at the top of playit,
+// before the command loop (main.c playit). It is split out so tests can
+// drive a bounded number of turns; the loop itself never returns,
+// because game-over exits the process.
+func (g *RogueGame) prePlay() {
 	// set up defaults for modern terminals: curses' md_hasclreol() is
 	// always true, so the C default inventory style applies
 	if !g.restored {
@@ -242,13 +250,7 @@ func (g *RogueGame) playit() {
 	}
 
 	g.Oldpos = g.Player.Pos
-
 	g.Oldrp = g.roomIn(g.Player.Pos)
-	for g.Playing {
-		g.command() // command execution
-	}
-
-	g.endit()
 }
 
 // endit exits the game (main.c endit).