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/dice.go

@@ -25,20 +25,26 @@ type DiceSpec []DiceRoll
 // a single 0x0 attack, as it did in C.
 func ParseDice(s string) DiceSpec {
 	var spec DiceSpec
+
 	for s != "" {
 		count := cAtoi(s)
+
 		xi := strings.IndexByte(s, 'x')
 		if xi < 0 {
 			break
 		}
+
 		s = s[xi+1:]
 		spec = append(spec, DiceRoll{Count: count, Sides: cAtoi(s)})
+
 		si := strings.IndexByte(s, '/')
 		if si < 0 {
 			break
 		}
+
 		s = s[si+1:]
 	}
+
 	return spec
 }
 
@@ -48,11 +54,14 @@ func dice(s string) DiceSpec { return ParseDice(s) }
 // String renders the spec back in the classic "NxM/NxM" form.
 func (d DiceSpec) String() string {
 	var sb strings.Builder
+
 	for i, r := range d {
 		if i > 0 {
 			sb.WriteByte('/')
 		}
+
 		fmt.Fprintf(&sb, "%dx%d", r.Count, r.Sides)
 	}
+
 	return sb.String()
 }