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>

TODO.md

@@ -529,11 +529,22 @@ box's left edge at x=100 is a solid white line (mean 255), the box interior is b
 outlines rather than fills — and an empty corner is black. stdout carried `HELLO WORLD` at the
 same time. `QUIT` exits cleanly with status 0.
 
-**What that check does not cover, and could not here:** typing at a real focused window. No key
-synthesis tool (`xdotool`, `xte`, python-xlib) is installed on this machine, so the keyboard
-path is proved only through SDL's own event queue in `tests/akgl_frontend.c` — which is the
-same queue a real keyboard delivers into, but not the same as a window manager giving the
-window focus. Somebody should type at it once.
+**The typing half is no longer manual, and it is no longer a gap.** It used to read "somebody
+should type at it once", because no key-synthesis tool was installed. `xdotool` now is, and
+`tests/akgl_typing.sh` is registered as the `akgl_typing` CTest case: it starts the driver under
+a pty, waits for the window with `xdotool search --sync`, gives it keyboard focus, types a
+program containing a **string literal** and a **lower-case** one, and polls the mirrored stdout
+for what they print.
+
+That case earns its keep twice over. It is the only test that covers the path *upstream* of SDL
+— X11 → SDL composition → libakgl's ring → the editor — and everything else synthesises SDL
+events, which is precisely how the missing `SDL_StartTextInput()` shipped with a green suite.
+Confirmed by reverting both halves of that fix and watching it fail with the same symptom that
+was reported: `READY`, and nothing after it.
+
+It needs a real X server, a window manager and `xdotool`, and it steals keyboard focus for about
+fifteen seconds. Absent any of those it reports CTest `Skipped` rather than failing, which is
+what it does in CI. `AKBASIC_SKIP_INTERACTIVE=1` skips it deliberately.
 
 ### The five things that had to be worked around — **all gone**
 
@@ -1122,7 +1133,7 @@ requirement; exactly one case has diverged on purpose since, and
 | Gate | Result |
 |---|---|
 | `ctest` | 77/77 — 41 reference golden cases, 9 local ones, 25 unit tests, 2 embedding examples. No known-failing tests: the list is empty |
-| `ctest` with `-DAKBASIC_WITH_AKGL=ON` | 76/76 — the same, minus the three `no_device` cases the SDL driver contradicts, plus `akgl_backends` and `akgl_frontend`; the `akgl_build` CI job |
+| `ctest` with `-DAKBASIC_WITH_AKGL=ON` | 77/77 on a machine with a display; 76 passed + 1 skipped headless. The same set minus the three `no_device` cases the SDL driver contradicts, plus `akgl_backends`, `akgl_frontend` and `akgl_typing` — the last of which is the skip, and the `akgl_build` CI job is where it skips |
 | Golden corpus | 41/41 byte-exact from `tests/reference/` — **and 41/41 again through the SDL binary**, which is most of what proves the frontend changes no output |
 | ASan + UBSan | 77/77 |
 | Line coverage | 94.6% (3857/4076) — above the 90% gate |