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/weapons.go

@@ -13,9 +13,11 @@ func (g *RogueGame) missile(ydelta, xdelta int) {
 	if obj == nil {
 		return
 	}
+
 	if !g.dropCheck(obj) || g.isCurrent(obj) {
 		return
 	}
+
 	obj = g.leavePack(obj, true, false)
 	g.doMotion(obj, ydelta, xdelta)
 	// AHA! Here it has hit something.  If it is a wall or a door, or if
@@ -39,11 +41,13 @@ func (g *RogueGame) doMotion(obj *Object, ydelta, xdelta int) {
 			if ch == Floor && !g.showFloor() {
 				ch = ' '
 			}
+
 			g.mvaddch(obj.Pos.Y, obj.Pos.X, ch)
 		}
 		// Get the new position
 		obj.Pos.Y += ydelta
 		obj.Pos.X += xdelta
+
 		ch := g.Level.VisibleChar(obj.Pos.Y, obj.Pos.X)
 		if stepOk(ch) && ch != Door {
 			// It hasn't hit anything yet, so display it if it's alright.
@@ -51,8 +55,10 @@ func (g *RogueGame) doMotion(obj *Object, ydelta, xdelta int) {
 				g.mvaddch(obj.Pos.Y, obj.Pos.X, obj.Kind.Glyph())
 				g.refresh()
 			}
+
 			continue
 		}
+
 		break
 	}
 }
@@ -62,6 +68,7 @@ func (g *RogueGame) fall(obj *Object, pr bool) {
 	if fpos, ok := g.fallpos(obj.Pos); ok {
 		pp := g.Level.At(fpos.Y, fpos.X)
 		pp.Ch = obj.Kind.Glyph()
+
 		obj.Pos = fpos
 		if g.cansee(fpos.Y, fpos.X) {
 			if pp.Monst != nil {
@@ -70,14 +77,18 @@ func (g *RogueGame) fall(obj *Object, pr bool) {
 				g.mvaddch(fpos.Y, fpos.X, obj.Kind.Glyph())
 			}
 		}
+
 		attachObj(&g.Level.Objects, obj)
+
 		return
 	}
+
 	if pr {
 		if g.HasHit {
 			g.endmsg()
 			g.HasHit = false
 		}
+
 		g.msg("the %s vanishes as it hits the ground",
 			g.Items.Weapons[obj.Which].Name)
 	}
@@ -92,32 +103,43 @@ func (g *RogueGame) hitMonster(mp Coord, obj *Object) bool {
 // wield pulls out a certain weapon (weapons.c wield).
 func (g *RogueGame) wield() {
 	p := &g.Player
+
 	oweapon := p.CurWeapon
 	if !g.dropCheck(p.CurWeapon) {
 		p.CurWeapon = oweapon
+
 		return
 	}
+
 	p.CurWeapon = oweapon
+
 	obj := g.getItem("wield", KindWeapon)
 	if obj == nil {
 		g.After = false
+
 		return
 	}
+
 	if obj.Kind == KindArmor {
 		g.msg("you can't wield armor")
 		g.After = false
+
 		return
 	}
+
 	if g.isCurrent(obj) {
 		g.After = false
+
 		return
 	}
 
 	sp := g.invName(obj, true)
 	p.CurWeapon = obj
+
 	if !g.Options.Terse {
-		g.addmsg("you are now ")
+		g.addmsgf("you are now ")
 	}
+
 	g.msg("wielding %s (%c)", sp, obj.PackCh)
 }
 
@@ -149,16 +171,19 @@ func (g *RogueGame) initWeapon(weap *Object, which WeaponKind) {
 	weap.Launch = iwp.launch
 	weap.Flags = iwp.flags
 	weap.HPlus = 0
+
 	weap.DPlus = 0
-	if which == WeaponDagger {
+
+	switch {
+	case which == WeaponDagger:
 		weap.Count = g.rnd(4) + 2
 		weap.Group = g.Items.Group
 		g.Items.Group++
-	} else if weap.Flags.Has(Stackable) {
+	case weap.Flags.Has(Stackable):
 		weap.Count = g.rnd(8) + 8
 		weap.Group = g.Items.Group
 		g.Items.Group++
-	} else {
+	default:
 		weap.Count = 1
 		weap.Group = 0
 	}
@@ -170,6 +195,7 @@ func num(n1, n2 int, typ byte) string {
 	if typ == Weapon {
 		out += fmt.Sprintf(",%+d", n2)
 	}
+
 	return out
 }
 
@@ -177,7 +203,9 @@ func num(n1, n2 int, typ byte) string {
 // (weapons.c fallpos).
 func (g *RogueGame) fallpos(pos Coord) (Coord, bool) {
 	var newpos Coord
+
 	cnt := 0
+
 	for y := pos.Y - 1; y <= pos.Y+1; y++ {
 		for x := pos.X - 1; x <= pos.X+1; x++ {
 			// check to make certain the spot is empty, if it is, put the
@@ -187,6 +215,7 @@ func (g *RogueGame) fallpos(pos Coord) (Coord, bool) {
 				y < 0 || x < 0 {
 				continue
 			}
+
 			ch := g.Level.Char(y, x)
 			if ch == Floor || ch == Passage {
 				if cnt++; g.rnd(cnt) == 0 {
@@ -196,5 +225,6 @@ func (g *RogueGame) fallpos(pos Coord) (Coord, bool) {
 			}
 		}
 	}
+
 	return newpos, cnt != 0
 }