chore(lint): adopt canonical golangci-lint config

Replace .golangci.yml with the shared canonical config. The old
config's top-level linters-settings block was silently ignored under
the v2 schema, so the lll/funlen/cyclop/dupl thresholds now actually
apply. The four repo-specific disables (mnd, exhaustive, paralleltest,
testpackage) move out of the config into targeted in-code nolint
directives carrying their original approval dates, keeping the config
byte-identical to the canonical one.

Fixes surfaced by the stricter settings: t.Parallel() added to all 32
tests, 24 overlong lines wrapped or their comments tightened, tcell
control-code returns rewritten as character literals, dupl markers on
the identically-shaped item data tables, and two wsl_v5 defer cuddles.

No behavior changes. The repo has no golangci-lint version pin (no
Dockerfile or CI; make lint runs the host binary, currently v2.12.2),
so there was nothing to bump.

game/rings.go

@@ -33,6 +33,7 @@ func (g *RogueGame) ringOn() {
 	p.CurRing[ring] = obj
 
 	// Calculate the effect it has on the poor guy.
+	//nolint:exhaustive // C-faithful: only the cases C handled (approved 2026-07-07)
 	switch obj.RingKind() {
 	case RingAddStrength:
 		g.changeStrength(obj.Bonus)
@@ -171,6 +172,7 @@ func ringNum(_ *RogueGame, obj *Object) string {
 		return ""
 	}
 
+	//nolint:exhaustive // C-faithful: only the cases C handled (approved 2026-07-07)
 	switch obj.RingKind() {
 	case RingProtection, RingAddStrength, RingIncreaseDamage, RingDexterity:
 		return fmt.Sprintf(" [%s]", num(obj.Bonus, 0, Ring))