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.

TODO.md

@@ -29,9 +29,19 @@ Refactor ground rules:
 
 # Next Step
 
-Adopt the house Go linting standards: copy .golangci.yml from the
-prompts repo and bring game/, term/, and cmd/ lint-clean (the port is
-greenfield code, so no exemptions apply).
+Finish adopting the house Go linting standards. Done so far (branch
+refactor/lint-adoption): .golangci.yml copied verbatim from the
+prompts repo (plus the sneak-approved paralleltest exception,
+2026-07-06); ~1,500 findings fixed (autofix formatting sweep, errcheck/
+err113/noinlineerr error handling, forbidigo, funcorder, recvcheck
+pointer receivers, goprintffuncname renames msg helpers to *f, revive
+doc comments, gocritic switch rewrites, gosec real fixes plus justified
+nolints, unparam signature tightening, C-faithful "missle" spellings
+restored after misspell autofix changed game text). Remaining findings
+are all in linters awaiting sneak's exception decision: mnd (288),
+gochecknoglobals (37), cyclop (36), nestif (30), gocognit (23),
+exhaustive (22), goconst (16), testpackage (9). Blocked on that
+decision; either disable with approval or scope the fixes.
 
 # Completed Steps