Reindent all C sources to the canonical stroustrup style

Mechanical whitespace-only change across src/, include/, tests/, and
util/, applied with scripts/reindent.sh. No behavioral change.

Most files already conformed. The genuine outliers indented at 2 columns
(json_helpers.c, util.c from akgl_rectangle_points onward, assets.c,
staticstring.c, akgl_actor_add_child, util.h, staticstring.h) or used
spaces where the canonical form is a tab (draw.c). cc-mode also re-aligns
line-continuation backslashes in multi-line macros to its default
c-backslash-column, which is required for the tree to be a fixed point of
the indenter.

Verified whitespace-only: `git diff -w` over this change is empty apart
from three trailing blank lines removed at EOF in src/heap.c,
src/registry.c, and tests/tilemap.c. The build produces no new errors and
ctest is unchanged at 13/14, with `character` still the one intentional
failure.

The tree is now a fixed point of `scripts/reindent.sh --check`.

include/akgl/SDL_GameControllerDB.h is generated and excluded.

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

include/akgl/error.h

@@ -10,11 +10,11 @@
 // e.g., combining two element of PATH_MAX into a string buffer of AKGL_STRING_MAX_LENGTH.
 // We have to draw a line in the sand somewhere or we will just let our buffers grow forever
 // to keep the compiler happy.
-#define DISABLE_GCC_WARNING_FORMAT_TRUNCATION	\
-    _Pragma("GCC diagnostic push") \
+#define DISABLE_GCC_WARNING_FORMAT_TRUNCATION			\
+    _Pragma("GCC diagnostic push")				\
     _Pragma("GCC diagnostic ignored \"-Wformat-truncation\"")
 
-#define RESTORE_GCC_WARNINGS \
+#define RESTORE_GCC_WARNINGS			\
     _Pragma("GCC diagnostic pop")
 
 #define AKGL_ERR_SDL               (AKERR_LAST_ERRNO_VALUE + 18)