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/io.go

@@ -31,16 +31,18 @@ func (g *RogueGame) msg(format string, a ...any) int {
 		g.move(0, 0)
 		g.clrtoeol()
 		g.Msgs.Mpos = 0
+
 		return ^Escape
 	}
 	// otherwise add to the message and flush it out
-	g.doadd(format, a...)
+	g.doaddf(format, a...)
+
 	return g.endmsg()
 }
 
-// addmsg adds things to the current message (io.c addmsg).
-func (g *RogueGame) addmsg(format string, a ...any) {
-	g.doadd(format, a...)
+// addmsgf adds things to the current message (io.c addmsg).
+func (g *RogueGame) addmsgf(format string, a ...any) {
+	g.doaddf(format, a...)
 }
 
 // endmsg displays a new msg, giving the player a chance to see the previous
@@ -50,10 +52,12 @@ func (g *RogueGame) endmsg() int {
 	if m.SaveMsg {
 		m.Huh = m.buf.String()
 	}
+
 	if m.Mpos != 0 {
 		g.look(false)
 		g.mvaddstr(0, m.Mpos, "--More--")
 		g.refresh()
+
 		if !m.MsgEsc {
 			g.waitFor(' ')
 		} else {
@@ -62,10 +66,12 @@ func (g *RogueGame) endmsg() int {
 				if ch == ' ' {
 					break
 				}
+
 				if ch == Escape {
 					m.buf.Reset()
 					m.Mpos = 0
 					m.newpos = 0
+
 					return Escape
 				}
 			}
@@ -75,25 +81,30 @@ func (g *RogueGame) endmsg() int {
 	// with a pack addressing character
 	out := m.buf.String()
 	if len(out) > 0 && isLower(out[0]) && !m.LowerMsg &&
-		!(len(out) > 1 && out[1] == ')') {
+		(len(out) <= 1 || out[1] != ')') {
 		out = string(toUpper(out[0])) + out[1:]
 	}
+
 	g.mvaddstr(0, 0, out)
 	g.clrtoeol()
+
 	m.Mpos = m.newpos
 	m.newpos = 0
 	m.buf.Reset()
 	g.refresh()
+
 	return ^Escape
 }
 
-// doadd performs an add onto the message buffer (io.c doadd).
-func (g *RogueGame) doadd(format string, a ...any) {
+// doaddf performs an add onto the message buffer (io.c doadd).
+func (g *RogueGame) doaddf(format string, a ...any) {
 	m := &g.Msgs
+
 	s := fmt.Sprintf(format, a...)
 	if len(s)+m.newpos >= maxMsg {
 		g.endmsg()
 	}
+
 	m.buf.WriteString(s)
 	m.newpos = m.buf.Len()
 }
@@ -114,8 +125,10 @@ func (g *RogueGame) readchar() byte {
 	ch := g.scr.term.ReadChar()
 	if ch == 3 { // ^C
 		g.quit(0)
+
 		return 27
 	}
+
 	return ch
 }
 
@@ -146,17 +159,21 @@ func (g *RogueGame) status() {
 	if p.CurArmor != nil {
 		temp = p.CurArmor.ArmorClass
 	}
+
 	if s.init && s.hp == p.Stats.HP && s.exp == p.Stats.Exp &&
 		s.pur == p.Purse && s.arm == temp && s.str == p.Stats.Str &&
 		s.lvl == g.Depth && s.hungry == p.HungryState && !g.StatMsg {
 		return
 	}
+
 	s.init = true
 	s.arm = temp
 
 	oy, ox := g.scr.Std.GetYX()
+
 	if s.hp != p.Stats.MaxHP {
 		s.hp = p.Stats.MaxHP
+
 		s.hpwidth = 0
 		for t := p.Stats.MaxHP; t != 0; t /= 10 {
 			s.hpwidth++
@@ -183,6 +200,7 @@ func (g *RogueGame) status() {
 		g.move(StatLine, 0)
 		g.addstr(line)
 	}
+
 	g.clrtoeol()
 	g.move(oy, ox)
 }
@@ -197,7 +215,11 @@ func (g *RogueGame) waitFor(ch byte) {
 			}
 		}
 	}
-	for g.readchar() != ch {
+
+	for {
+		if g.readchar() == ch {
+			return
+		}
 	}
 }
 
@@ -221,11 +243,13 @@ func toUpper(c byte) byte {
 	if isLower(c) {
 		return c - 'a' + 'A'
 	}
+
 	return c
 }
 func toLower(c byte) byte {
 	if isUpper(c) {
 		return c - 'A' + 'a'
 	}
+
 	return c
 }