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>
Co-Authored-By: Andrew Kesterson <andrew@aklabs.net>

src/text.c

@@ -10,7 +10,7 @@
 #include <akgl/registry.h>
 #include <akgl/game.h>
 
-akerr_ErrorContext AKERR_NOIGNORE *akgl_text_loadfont(char *name, char *filepath, int size)
+akerr_ErrorContext *akgl_text_loadfont(char *name, char *filepath, int size)
 {
     TTF_Font *font = NULL;
 
@@ -37,7 +37,7 @@ akerr_ErrorContext AKERR_NOIGNORE *akgl_text_loadfont(char *name, char *filepath
     SUCCEED_RETURN(errctx);
 }
 
-akerr_ErrorContext AKERR_NOIGNORE *akgl_text_unloadfont(char *name)
+akerr_ErrorContext *akgl_text_unloadfont(char *name)
 {
     TTF_Font *font = NULL;
 
@@ -54,7 +54,7 @@ akerr_ErrorContext AKERR_NOIGNORE *akgl_text_unloadfont(char *name)
     SUCCEED_RETURN(errctx);
 }
 
-akerr_ErrorContext AKERR_NOIGNORE *akgl_text_rendertextat(TTF_Font *font, char *text, SDL_Color color, int wraplength, int x, int y)
+akerr_ErrorContext *akgl_text_rendertextat(TTF_Font *font, char *text, SDL_Color color, int wraplength, int x, int y)
 {
     SDL_Surface *textsurf = NULL;
     SDL_Texture *texture = NULL;
@@ -96,7 +96,7 @@ akerr_ErrorContext AKERR_NOIGNORE *akgl_text_rendertextat(TTF_Font *font, char *
     SUCCEED_RETURN(errctx);
 }
 
-akerr_ErrorContext AKERR_NOIGNORE *akgl_text_measure(TTF_Font *font, char *text, int *w, int *h)
+akerr_ErrorContext *akgl_text_measure(TTF_Font *font, char *text, int *w, int *h)
 {
     PREPARE_ERROR(errctx);
     FAIL_ZERO_RETURN(errctx, font, AKERR_NULLPOINTER, "NULL font");
@@ -114,7 +114,7 @@ akerr_ErrorContext AKERR_NOIGNORE *akgl_text_measure(TTF_Font *font, char *text,
     SUCCEED_RETURN(errctx);
 }
 
-akerr_ErrorContext AKERR_NOIGNORE *akgl_text_measure_wrapped(TTF_Font *font, char *text, int wraplength, int *w, int *h)
+akerr_ErrorContext *akgl_text_measure_wrapped(TTF_Font *font, char *text, int wraplength, int *w, int *h)
 {
     PREPARE_ERROR(errctx);
     FAIL_ZERO_RETURN(errctx, font, AKERR_NULLPOINTER, "NULL font");