Adopt house golangci-lint config; fix all approved-linter findings

.golangci.yml is the prompts-repo standard verbatim plus one approved
exception (paralleltest, sneak 2026-07-06). Roughly 1,500 findings
fixed:

- autofix sweep (wsl_v5/nlreturn/intrange/modernize formatting), with
  the misspell autofix REVERTED where it rewrote authentic C game text
  ("missle vanishes" stays, with nolint and a comment)
- error handling: errcheck sites get real handling — saveFile now
  closes explicitly and removes corrupt saves, scoreboard writes are
  documented best-effort, err113 sentinel errors (ErrSaveOutOfDate,
  ErrScreenTooSmall); panics allowed for unrecoverable states per
  MEMORY.md policy
- gosec: real fixes (ParseInt for SEED, 0600 scorefile) and justified
  per-line nolints for provably-bounded conversions (randomMonsterLetter
  helper collapses eight rnd(26)+'A' sites)
- API tidying from linters: pointer receivers on flag types
  (recvcheck), msg helpers renamed addmsgf/doaddf/Printwf/MvPrintwf
  (goprintffuncname), myExit()/findFloor(monst)/mkGameInput(t) drop
  always-constant params (unparam), gameEnd carries no status
- gocritic/staticcheck: if-else chains to switches, the pack.c
  inventory filter untangled into matchesFilter, main.go split so
  defers run before exit (exitAfterDefer, funlen)
- revive doc comments on all exported flag types/consts/methods

Remaining findings are confined to linters pending sneak's exception
decision (mnd, gochecknoglobals, cyclop, nestif, gocognit, exhaustive,
goconst, testpackage); TODO.md records the state. MEMORY.md added at
repo root as the project's agent working notes.

game/newlevel.go

@@ -13,6 +13,7 @@ const (
 func (g *RogueGame) NewLevel() {
 	p := &g.Player
 	p.Flags.Clear(Held) // unhold when you go down just in case
+
 	if g.Depth > g.MaxDepth {
 		g.MaxDepth = g.Depth
 	}
@@ -20,6 +21,7 @@ func (g *RogueGame) NewLevel() {
 	for i := range g.Level.Places {
 		g.Level.Places[i] = Place{Ch: ' ', Flags: FReal}
 	}
+
 	g.clear()
 	// Free up the monsters on the last level; the objects and their packs
 	// go with them (the garbage collector is our free_list).
@@ -27,32 +29,33 @@ func (g *RogueGame) NewLevel() {
 	g.Level.Objects = nil
 	g.doRooms()    // Draw rooms
 	g.doPassages() // Draw passages
+
 	p.NoFood++
+
 	g.putThings() // Place objects (if any)
 	// Place the traps
 	if g.rnd(10) < g.Depth {
-		g.Level.TrapCount = g.rnd(g.Depth/4) + 1
-		if g.Level.TrapCount > MaxTraps {
-			g.Level.TrapCount = MaxTraps
-		}
+		g.Level.TrapCount = min(g.rnd(g.Depth/4)+1, MaxTraps)
+
 		for i := g.Level.TrapCount; i > 0; i-- {
 			// not only wouldn't it be NICE to have traps in mazes (not
 			// that we care about being nice), since the trap number is
 			// stored where the passage number is, we can't actually do it.
 			var stairs Coord
 			for {
-				stairs, _ = g.findFloor(nil, 0, false)
+				stairs, _ = g.findFloor(false)
 				if g.Level.Char(stairs.Y, stairs.X) == Floor {
 					break
 				}
 			}
+
 			sp := g.Level.FlagsAt(stairs.Y, stairs.X)
 			sp.Clear(FReal)
-			*sp |= PlaceFlags(g.rnd(NumTrapTypes))
+			*sp |= PlaceFlags(g.rnd(NumTrapTypes)) //nolint:gosec // G115: 0..7 fits
 		}
 	}
 	// Place the staircase down.
-	stairs, _ := g.findFloor(nil, 0, false)
+	stairs, _ := g.findFloor(false)
 	g.Level.Stairs = stairs
 	g.Level.SetChar(stairs.Y, stairs.X, Stairs)
 	g.SeenStairs = false
@@ -61,13 +64,15 @@ func (g *RogueGame) NewLevel() {
 		tp.Room = g.roomin(tp.Pos)
 	}
 
-	hero, _ := g.findFloor(nil, 0, true)
+	hero, _ := g.findFloor(true)
 	p.Pos = hero
 	g.enterRoom(hero)
 	g.mvaddch(hero.Y, hero.X, PlayerCh)
+
 	if p.On(SenseMonsters) {
 		g.turnSee(false)
 	}
+
 	if p.On(Hallucinating) {
 		g.visuals(0)
 	}
@@ -96,13 +101,13 @@ func (g *RogueGame) putThings() {
 		g.treasRoom()
 	}
 	// Do MAXOBJ attempts to put things on a level
-	for i := 0; i < MaxObj; i++ {
+	for range MaxObj {
 		if g.rnd(100) < 36 {
 			// Pick a new object and link it in the list
 			obj := g.newThing()
 			attachObj(&g.Level.Objects, obj)
 			// Put it somewhere
-			obj.Pos, _ = g.findFloor(nil, 0, false)
+			obj.Pos, _ = g.findFloor(false)
 			g.Level.SetChar(obj.Pos.Y, obj.Pos.X, obj.Kind.Glyph())
 		}
 	}
@@ -116,7 +121,7 @@ func (g *RogueGame) putThings() {
 		obj.ArmorClass = 11
 		obj.Kind = KindAmulet
 		// Put it somewhere
-		obj.Pos, _ = g.findFloor(nil, 0, false)
+		obj.Pos, _ = g.findFloor(false)
 		g.Level.SetChar(obj.Pos.Y, obj.Pos.X, Amulet)
 	}
 }
@@ -124,10 +129,9 @@ func (g *RogueGame) putThings() {
 // treasRoom adds a treasure room (new_level.c treas_room).
 func (g *RogueGame) treasRoom() {
 	rp := &g.Level.Rooms[g.rndRoom()]
-	spots := (rp.Max.Y-2)*(rp.Max.X-2) - minTreas
-	if spots > maxTreas-minTreas {
-		spots = maxTreas - minTreas
-	}
+
+	spots := min((rp.Max.Y-2)*(rp.Max.X-2)-minTreas, maxTreas-minTreas)
+
 	numMonst := g.rnd(spots) + minTreas
 	for nm := numMonst; nm > 0; nm-- {
 		mp, _ := g.findFloorIn(rp, 2*maxTries, false)
@@ -138,14 +142,13 @@ func (g *RogueGame) treasRoom() {
 	}
 
 	// fill up room with monsters from the next level down
-	nm := g.rnd(spots) + minTreas
-	if nm < numMonst+2 {
-		nm = numMonst + 2
-	}
+	nm := max(g.rnd(spots)+minTreas, numMonst+2)
+
 	spots = (rp.Max.Y - 2) * (rp.Max.X - 2)
 	if nm > spots {
 		nm = spots
 	}
+
 	g.Depth++
 	for ; nm > 0; nm-- {
 		if mp, ok := g.findFloorIn(rp, maxTries, true); ok {
@@ -155,5 +158,6 @@ func (g *RogueGame) treasRoom() {
 			g.givePack(tp)
 		}
 	}
+
 	g.Depth--
 }