Take libakgl 0.9.0, and shadow set_property(TEST) so it configures

0.9.0 is the akgl_ui subsystem: a vendored clay, an arena, menus, HUDs and
dialogs, reached through a new akgl/ui.h this project does not include. Every
header the akbasic_akgl target actually compiles against is byte-identical to
0.8.0, so unlike the 0.8.0 bump there is no sizeof to get wrong. The floor in
include/akbasic/akgl.h moves to 0.9.0 anyway, on the standing rule that the
soname carries MAJOR.MINOR while the major is 0.

It does not configure as it stands. 0.9.0 moved eight test property calls off
set_tests_properties -- correctly, because that command splits a
semicolon-separated value and had been silently reducing its LD_LIBRARY_PATH
prepend list to one directory -- onto set_property(TEST ...). This repository
suppresses add_test() while it pulls its dependencies in, so those test names do
not exist, and set_property errors on an unknown test name where
set_tests_properties was silent: eight hard configure failures. Shadow
set_property in its TEST form only; every other form has to pass through, since
the dependencies set target and directory properties their own builds need.

libakgl's status band grew to seven codes with AKGL_ERR_UI and it now owns 256
to 262, so the coordinated range map, docs/15-error-codes.md and both header
comments follow. TODO.md section 5's persistent-drawing-layer item still stands:
0.9.0's arena draws inside the frame like everything else, and there is still no
render-to-texture layer.

Both configurations build and both suites pass -- 110/110 without libakgl,
111/111 with it, akgl_typing included.

Co-Authored-By: Tachikoma (Claude Code Opus 5 1M) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EwxGB6TdoVvZ11KQQME9cL
Co-Authored-By: Andrew Kesterson <andrew@aklabs.net>

docs/15-error-codes.md

@@ -123,7 +123,7 @@ just above the `errno` range, and they surface when something fails below the la
 rather than in it — `SCRATCH` on a file that will not delete gives its
 `Input Output Error`, and `VAL` of text that is not a number gives its `Value Error`
 rather than the interpreter's 517, because the conversion happens in `libakstdlib` and
-the code comes back up with it. In the SDL build, `libakgl` owns 256 to 261 and an
+the code comes back up with it. In the SDL build, `libakgl` owns 256 to 262 and an
 `SDL Error` can reach `ER#` if the renderer itself refuses.
 
 **Do not hardcode those numbers.** `libakerror`'s codes are defined as offsets from