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/screen.go

@@ -37,26 +37,28 @@ type Window struct {
 func NewWindow(rows, cols int) *Window {
 	w := &Window{rows: rows, cols: cols, cells: make([]cell, rows*cols)}
 	w.Clear()
+
 	return w
 }
 
-func (w *Window) at(y, x int) *cell { return &w.cells[y*w.cols+x] }
-
 // Move positions the cursor (curses move/wmove).
 func (w *Window) Move(y, x int) { w.cy, w.cx = y, x }
 
 // GetYX reports the cursor position (curses getyx).
-func (w *Window) GetYX() (y, x int) { return w.cy, w.cx }
+func (w *Window) GetYX() (int, int) { return w.cy, w.cx }
 
 // AddCh writes a character at the cursor and advances it (curses addch).
 func (w *Window) AddCh(ch byte) {
 	if ch == '\n' {
 		w.cy, w.cx = w.cy+1, 0
+
 		return
 	}
+
 	if w.cy < 0 || w.cy >= w.rows || w.cx < 0 || w.cx >= w.cols {
 		return
 	}
+
 	*w.at(w.cy, w.cx) = cell{ch: ch, standout: w.standout}
 	if w.cx++; w.cx >= w.cols {
 		w.cx = 0
@@ -68,7 +70,7 @@ func (w *Window) AddCh(ch byte) {
 
 // AddStr writes a string at the cursor (curses addstr).
 func (w *Window) AddStr(s string) {
-	for i := 0; i < len(s); i++ {
+	for i := range len(s) {
 		w.AddCh(s[i])
 	}
 }
@@ -85,15 +87,15 @@ func (w *Window) MvAddStr(y, x int, s string) {
 	w.AddStr(s)
 }
 
-// Printw writes formatted text at the cursor (curses printw).
-func (w *Window) Printw(format string, a ...any) {
+// Printwf writes formatted text at the cursor (curses printw).
+func (w *Window) Printwf(format string, a ...any) {
 	w.AddStr(fmt.Sprintf(format, a...))
 }
 
-// MvPrintw moves then writes formatted text (curses mvprintw).
-func (w *Window) MvPrintw(y, x int, format string, a ...any) {
+// MvPrintwf moves then writes formatted text (curses mvprintw).
+func (w *Window) MvPrintwf(y, x int, format string, a ...any) {
 	w.Move(y, x)
-	w.Printw(format, a...)
+	w.Printwf(format, a...)
 }
 
 // Inch returns the character under the cursor (curses inch, sans
@@ -102,12 +104,14 @@ func (w *Window) Inch() byte {
 	if w.cy < 0 || w.cy >= w.rows || w.cx < 0 || w.cx >= w.cols {
 		return ' '
 	}
+
 	return w.at(w.cy, w.cx).ch
 }
 
 // MvInch moves then reads (curses mvinch).
 func (w *Window) MvInch(y, x int) byte {
 	w.Move(y, x)
+
 	return w.Inch()
 }
 
@@ -120,6 +124,7 @@ func (w *Window) Clear() {
 	for i := range w.cells {
 		w.cells[i] = cell{ch: ' '}
 	}
+
 	w.cy, w.cx = 0, 0
 }
 
@@ -128,6 +133,7 @@ func (w *Window) Clrtoeol() {
 	if w.cy < 0 || w.cy >= w.rows {
 		return
 	}
+
 	for x := w.cx; x < w.cols; x++ {
 		*w.at(w.cy, x) = cell{ch: ' '}
 	}
@@ -138,13 +144,14 @@ func (w *Window) CopyFrom(src *Window) {
 	copy(w.cells, src.cells)
 }
 
-// Size reports the window dimensions.
-func (w *Window) Size() (rows, cols int) { return w.rows, w.cols }
+// Size reports the window dimensions as rows, columns.
+func (w *Window) Size() (int, int) { return w.rows, w.cols }
 
 // CellAt reports the character and standout attribute at a position; used
 // by Terminal implementations to render the window.
-func (w *Window) CellAt(y, x int) (ch byte, standout bool) {
+func (w *Window) CellAt(y, x int) (byte, bool) {
 	c := w.at(y, x)
+
 	return c.ch, c.standout
 }
 
@@ -155,6 +162,7 @@ func (w *Window) Contents() []byte {
 	for i, c := range w.cells {
 		out[i] = c.ch
 	}
+
 	return out
 }
 
@@ -171,12 +179,16 @@ func (w *Window) SetContents(data []byte) {
 // victory screens.
 func (w *Window) Line(y int) string {
 	buf := make([]byte, w.cols)
-	for x := 0; x < w.cols; x++ {
+	for x := range w.cols {
 		buf[x] = w.at(y, x).ch
 	}
+
 	return string(buf)
 }
 
+// at addresses the cell at (y, x) in the backing array.
+func (w *Window) at(y, x int) *cell { return &w.cells[y*w.cols+x] }
+
 // Screen bundles the two windows the game draws on with the device that
 // shows them.
 type Screen struct {
@@ -217,7 +229,7 @@ func (g *RogueGame) mvaddch(y, x int, c byte) { g.scr.Std.MvAddCh(y, x, c) }
 func (g *RogueGame) mvaddstr(y, x int, s string) {
 	g.scr.Std.MvAddStr(y, x, s)
 }
-func (g *RogueGame) printw(f string, a ...any) { g.scr.Std.Printw(f, a...) }
+func (g *RogueGame) printw(f string, a ...any) { g.scr.Std.Printwf(f, a...) }
 func (g *RogueGame) inch() byte                { return g.scr.Std.Inch() }
 func (g *RogueGame) mvinch(y, x int) byte      { return g.scr.Std.MvInch(y, x) }
 func (g *RogueGame) standout()                 { g.scr.Std.Standout(true) }