Type at the window with a real keyboard: the akgl_typing test

xdotool closes the gap that shipped the missing SDL_StartTextInput(). Every
other keyboard test synthesises SDL events, which covers the code downstream
of SDL and cannot cover the code upstream of it -- so the suite stayed green
while the real keyboard was dead.

akgl_typing starts the driver under a pty, waits for the window with xdotool
search --sync, gives it focus, and types a program containing a string literal
and a lower-case one, polling the mirrored stdout for what they print. Verified
by reverting both halves of the text-input fix and watching it fail with the
reported symptom: READY, and nothing after it.

Skips rather than fails without a display, xdotool, script(1) or a window
manager -- none of those means the answer is no. It steals keyboard focus for
about fifteen seconds; AKBASIC_SKIP_INTERACTIVE=1 skips it deliberately.

xdotool and script(1) are documented as optional test dependencies, alongside
what gcovr and python3 already bought.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -265,6 +265,12 @@ ctest --test-dir build --output-on-failure
 ctest --test-dir build -R <name> --output-on-failure   # single test
 ```
 
+**Optional test tooling for this repository.** `xdotool` and `script`(1) drive the `akgl_typing`
+test, which types at a real focused SDL window -- the only test that covers the path upstream of
+SDL, and the one that would have caught the missing `SDL_StartTextInput()`. It needs a real X
+server, steals keyboard focus for about fifteen seconds, and skips itself (CTest `Skipped`, not
+a failure) when it cannot run. `AKBASIC_SKIP_INTERACTIVE=1` skips it deliberately.
+
 Extra harnesses, by library (option prefixes differ per repo):
 
 ```sh