Give every exported function a declaration, and check that it stays that way

Closes internal-consistency items 7 through 15. Nineteen non-static functions
were in the ABI with no declaration anywhere, so no consumer could call them
and any consumer could collide with them.

The four gamepad_handle_* functions are the ones that mattered: controller.h
declared akgl_controller_handle_button_down and three siblings that did not
exist, so anything compiled against the header alone failed to link. The
definitions carry the declared names now, which also closes Defects -> Known
and still open item 10, and their documentation moved to the header.

The rest are either declared under a "part of the internal API" block --
akgl_game_save_actors and akgl_game_load_versioncmp, which tests/game.c had to
declare for itself, plus six tilemap loader helpers the untested-loader work
wants to reach -- or static, which is what the four save iterators and
load_objectnamemap should always have been. akgl_path_relative_from is deleted:
declared nowhere, called from nowhere, never wrote its output, and leaked a
pooled string on every call, so it closes Known and still open item 4 and item
40 by ceasing to exist.

scripts/check_api_surface.sh keeps it closed. It reads the built library's
dynamic symbol table and every public header with comments stripped, and fails
on an exported akgl_* symbol that is declared nowhere. Stripping comments is
the whole point -- four of these were mentioned in controller.h prose, which is
how they went unnoticed.

The pool-size ceilings are defined once, in heap.h, so the #ifndef override
hook fires for the first time; actor.h, sprite.h and character.h were defining
the same four unconditionally from headers heap.h includes above its own guard.
tests/header_pool_override.c fails the compile if that regresses.

Also here: (void) rather than () on the twelve no-argument entry points,
AKERR_NOIGNORE only on declarations, static helpers with the akgl_ prefix
dropped, and the six parameter-name mismatches. akgl_get_json_with_default had
its two contexts swapped rather than merely misspelled -- the incoming one was
`err` and its own was `e`, which is the name reserved for an incoming one.

24/24 pass, reindent --check clean.

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

src/draw.c

@@ -236,7 +236,7 @@ static akerr_ErrorContext *flood_region(SDL_Surface *surface, int x, int y, uint
     SUCCEED_RETURN(errctx);
 }
 
-akerr_ErrorContext AKERR_NOIGNORE *akgl_draw_point(akgl_RenderBackend *self, float32_t x, float32_t y, SDL_Color color)
+akerr_ErrorContext *akgl_draw_point(akgl_RenderBackend *self, float32_t x, float32_t y, SDL_Color color)
 {
     SDL_Color previous;
 
@@ -258,7 +258,7 @@ akerr_ErrorContext AKERR_NOIGNORE *akgl_draw_point(akgl_RenderBackend *self, flo
     SUCCEED_RETURN(errctx);
 }
 
-akerr_ErrorContext AKERR_NOIGNORE *akgl_draw_line(akgl_RenderBackend *self, float32_t x1, float32_t y1, float32_t x2, float32_t y2, SDL_Color color)
+akerr_ErrorContext *akgl_draw_line(akgl_RenderBackend *self, float32_t x1, float32_t y1, float32_t x2, float32_t y2, SDL_Color color)
 {
     SDL_Color previous;
 
@@ -280,7 +280,7 @@ akerr_ErrorContext AKERR_NOIGNORE *akgl_draw_line(akgl_RenderBackend *self, floa
     SUCCEED_RETURN(errctx);
 }
 
-akerr_ErrorContext AKERR_NOIGNORE *akgl_draw_rect(akgl_RenderBackend *self, SDL_FRect *rect, SDL_Color color)
+akerr_ErrorContext *akgl_draw_rect(akgl_RenderBackend *self, SDL_FRect *rect, SDL_Color color)
 {
     SDL_Color previous;
 
@@ -303,7 +303,7 @@ akerr_ErrorContext AKERR_NOIGNORE *akgl_draw_rect(akgl_RenderBackend *self, SDL_
     SUCCEED_RETURN(errctx);
 }
 
-akerr_ErrorContext AKERR_NOIGNORE *akgl_draw_filled_rect(akgl_RenderBackend *self, SDL_FRect *rect, SDL_Color color)
+akerr_ErrorContext *akgl_draw_filled_rect(akgl_RenderBackend *self, SDL_FRect *rect, SDL_Color color)
 {
     SDL_Color previous;
 
@@ -326,7 +326,7 @@ akerr_ErrorContext AKERR_NOIGNORE *akgl_draw_filled_rect(akgl_RenderBackend *sel
     SUCCEED_RETURN(errctx);
 }
 
-akerr_ErrorContext AKERR_NOIGNORE *akgl_draw_circle(akgl_RenderBackend *self, float32_t x, float32_t y, float32_t radius, SDL_Color color)
+akerr_ErrorContext *akgl_draw_circle(akgl_RenderBackend *self, float32_t x, float32_t y, float32_t radius, SDL_Color color)
 {
     SDL_Color previous;
     SDL_FPoint octants[8];
@@ -393,7 +393,7 @@ akerr_ErrorContext AKERR_NOIGNORE *akgl_draw_circle(akgl_RenderBackend *self, fl
     SUCCEED_RETURN(errctx);
 }
 
-akerr_ErrorContext AKERR_NOIGNORE *akgl_draw_flood_fill(akgl_RenderBackend *self, int x, int y, SDL_Color color)
+akerr_ErrorContext *akgl_draw_flood_fill(akgl_RenderBackend *self, int x, int y, SDL_Color color)
 {
     SDL_Surface *target = NULL;
     SDL_Surface *rgba = NULL;
@@ -481,7 +481,7 @@ akerr_ErrorContext AKERR_NOIGNORE *akgl_draw_flood_fill(akgl_RenderBackend *self
     SUCCEED_RETURN(errctx);
 }
 
-akerr_ErrorContext AKERR_NOIGNORE *akgl_draw_copy_region(akgl_RenderBackend *self, SDL_Rect *src, SDL_Surface **dest)
+akerr_ErrorContext *akgl_draw_copy_region(akgl_RenderBackend *self, SDL_Rect *src, SDL_Surface **dest)
 {
     SDL_Surface *saved = NULL;
     int width = 0;
@@ -551,7 +551,7 @@ akerr_ErrorContext AKERR_NOIGNORE *akgl_draw_copy_region(akgl_RenderBackend *sel
     SUCCEED_RETURN(errctx);
 }
 
-akerr_ErrorContext AKERR_NOIGNORE *akgl_draw_paste_region(akgl_RenderBackend *self, SDL_Surface *src, float32_t x, float32_t y)
+akerr_ErrorContext *akgl_draw_paste_region(akgl_RenderBackend *self, SDL_Surface *src, float32_t x, float32_t y)
 {
     SDL_Texture *patch = NULL;
     SDL_FRect dest;