docs: correct stale claims in MEMORY.md, TODO.md, and README.md (closes #3)

Four documented claims had gone false and were actively misdirecting agents
working this repo; the independent reviewer on PR #9 repeated one of them
verbatim. Each claim was re-verified against the tree before rewriting.

MEMORY.md "Error handling" described C's exit() calls being unwound by a
gameEnd panic recovered in Run. Refactor step 8 removed that: gameEnd appears
nowhere in the sources, myExit (game/rip.go) restores the terminal via
Terminal.Fini and calls os.Exit(0), and Run() has no return values and never
returns. The section now states that model and its testing consequence -- a
death exits the test binary, which is why tests drive command() directly and
crash sweeps pin the hero with fortify() in game/run_test.go.

MEMORY.md "Linting" said approved exceptions are recorded in a "Repo-specific
exceptions" block in .golangci.yml. There is no such block: the config is
byte-identical to canonical (sha256 021cc83f...46bcb) and the approvals live in
in-code //nolint directives carrying their dates. Following the old text would
have meant editing the canonical config. The same paragraph listed paralleltest
as an approved disable when it was fixed instead -- no paralleltest token
exists in the tree and all 32 tests call t.Parallel().

MEMORY.md "Debugging" and README.md both told the reader to run go test
directly. Since PR #9 the test target carries -timeout 30s -race -cover, so a
raw invocation silently drops the race detector while appearing to verify the
change. Both now point at make test / make check.

TODO.md asserted the host golangci-lint is "currently v2.12.2". It is v2.10.1
and the repo pins nothing, so the claim documented an accident of one machine.
Only the false claim is removed; the pin question is tracked separately.

Documentation only: no code, Makefile, or config change. Next Step is
deliberately not rotated, per the precedent for out-of-band issue work.

README.md

@@ -72,13 +72,15 @@ term/        tcell-backed terminal, replacing curses
 cmd/rogue/   the executable
 ```
 
-The engine package is fully headless-testable: `go test ./game/` runs scripted
-command sequences, dungeon-generation golden checks, and an RNG compatibility
-test against the original C generator.
+The engine package is fully headless-testable: `make test` runs scripted command
+sequences, dungeon-generation golden checks, and an RNG compatibility test
+against the original C generator.
 
 For development, the `Makefile` wraps the toolchain: `make fmt` (gofmt +
-prettier), `make lint` (golangci-lint), `make test`, and `make check` (all
-three).
+prettier), `make lint` (golangci-lint), `make test` (the suite, under the race
+detector with coverage and a timeout), and `make check` (all three). Use the
+targets rather than invoking `go test` directly — they carry the flags the
+project relies on.
 
 ## License