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/tables_test.go

@@ -9,8 +9,10 @@ func TestProbabilitiesSumTo100(t *testing.T) {
 		for _, oi := range info {
 			s += oi.Prob
 		}
+
 		return s
 	}
+
 	tables := map[string][]ObjInfo{
 		"things":  baseThings[:],
 		"potions": basePotInfo[:],
@@ -29,10 +31,12 @@ func TestProbabilitiesSumTo100(t *testing.T) {
 
 func TestInitProbsCumulative(t *testing.T) {
 	g := NewGame(Config{Seed: 1})
+
 	last := g.Items.Potions[NumPotionTypes-1].Prob
 	if last != 100 {
 		t.Errorf("cumulative potion probability ends at %d, want 100", last)
 	}
+
 	for i := PotionKind(1); i < NumPotionTypes; i++ {
 		if g.Items.Potions[i].Prob < g.Items.Potions[i-1].Prob {
 			t.Errorf("potion probs not nondecreasing at %d", i)
@@ -43,27 +47,34 @@ func TestInitProbsCumulative(t *testing.T) {
 func TestNewGameRandomizesAppearances(t *testing.T) {
 	g := NewGame(Config{Seed: 12345})
 	seen := map[string]bool{}
+
 	for i, c := range g.Items.PotColors {
 		if c == "" {
 			t.Fatalf("potion %d has no color", i)
 		}
+
 		if seen[c] {
 			t.Errorf("potion color %q assigned twice", c)
 		}
+
 		seen[c] = true
 	}
+
 	for i, n := range g.Items.ScrNames {
 		if n == "" {
 			t.Fatalf("scroll %d has no name", i)
 		}
+
 		if len(n) > MaxNameLen+1 {
 			t.Errorf("scroll name %q longer than C buffer allows", n)
 		}
 	}
+
 	for i := range g.Items.WandType {
 		if g.Items.WandType[i] != "wand" && g.Items.WandType[i] != "staff" {
 			t.Errorf("stick %d has type %q", i, g.Items.WandType[i])
 		}
+
 		if g.Items.WandMade[i] == "" {
 			t.Errorf("stick %d has no material", i)
 		}
@@ -80,6 +91,7 @@ func TestMonsterTable(t *testing.T) {
 	if monsterTable[0].Name != "aquator" || monsterTable[25].Name != "zombie" {
 		t.Error("monster table order broken")
 	}
+
 	if monsterTable['D'-'A'].Name != "dragon" {
 		t.Error("letter indexing broken")
 	}