Namespace every exported symbol, and bump to 0.5.0

Closes internal-consistency items 1 through 6, 12 and 13. Every include guard
is _AKGL_<FILE>_H_, every in-project header include is angled, and every
exported function, type and global carries the akgl_ prefix. This is an ABI
break; the soname goes to libakgl.so.0.5. TODO.md carries the full rename
table.

The renames were driven by renaming each declaration and letting the compiler
find the uses, not by pattern substitution: renderer, physics and camera are
also parameter and struct-member names, and a sed would have rewritten
map->physics and every akgl_RenderBackend *renderer parameter without a word.

Item 4 turned out not to be cosmetic. The library exported a global called
renderer and tests/character.c defined an SDL_Renderer *renderer of its own;
the executable's definition preempted the library's, akgl_sprite_load_json
read a SDL_Renderer * through an akgl_RenderBackend *, and every texture load
in that suite failed. The suite reported success anyway, because libakerror's
unhandled-error handler ends in exit(errctx->status), exit keeps only the low
byte, and AKGL_ERR_SDL is exactly 256. So character had been green while
running one of its four tests, and every suite in the tree was unable to fail
on the most common status in a library built on SDL.

Both are fixed. tests/testutil.h gains TEST_TRAP_UNHANDLED_ERRORS(), which
collapses any status a byte cannot carry onto 1, and every suite installs it.
character binds a real backend with akgl_render_2d_bind. Its fourth test then
runs for the first time and fails on a defect it has asserted all along, so
akgl_heap_release_character now walks state_sprites with
AKGL_ITERATOR_OP_RELEASE and destroys the property set before zeroing the slot
-- TODO.md Defects item 21 and half of Carried over item 1.

AKGL_TIME_ONESEC_MS said "one second in milliseconds" and held 1000000, so
akgl_game_state_lock waited roughly sixteen minutes rather than one second. It
is AKGL_TIME_ONEMS_NS now, the budget is its own named constant, and
tests/game.c holds the mutex from a second thread to assert the wait -- the
contended path had no coverage at all.

Headers are self-contained and it is enforced: AKGL_PUBLIC_HEADERS drives both
install() and a generated translation unit per header, so a header that ships
is a header that is checked. Writing that found registry.h, which used
SDL_PropertiesID in eight declarations and included no SDL header.

23/23 suites pass, memcheck is clean, reindent --check is clean.

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

include/akgl/actor.h

@@ -33,8 +33,8 @@
 #define _AKGL_ACTOR_H_
 
 #include <stdint.h>
-#include "types.h"
-#include "character.h"
+#include <akgl/types.h>
+#include <akgl/character.h>
 
 //           ---- LOW WORD STATUSES ----
 
@@ -225,7 +225,7 @@ akerr_ErrorContext AKERR_NOIGNORE *akgl_actor_set_character(akgl_Actor *obj, cha
  * @return `NULL` on success -- including every skipped case above -- otherwise
  *         an error context owned by the caller.
  * @throws AKERR_NULLPOINTER If @p obj or `obj->basechar` is `NULL`.
- * @throws AKERR_* Whatever akgl_sprite_sheet_coords_for_frame or the renderer's
+ * @throws AKERR_* Whatever akgl_spritesheet_coords_for_frame or the renderer's
  *         `draw_texture` raises.
  *
  * @note The destination height is computed from the sprite's *width*, so a
@@ -368,7 +368,7 @@ akerr_ErrorContext AKERR_NOIGNORE *akgl_actor_add_child(akgl_Actor *obj, akgl_Ac
  * @return `NULL` on success, otherwise an error context owned by the caller.
  * @throws AKERR_NULLPOINTER If @p obj, @p event, or `obj->basechar` is `NULL`.
  */
-akerr_ErrorContext AKERR_NOIGNORE *akgl_Actor_cmhf_left_on(akgl_Actor *obj, SDL_Event *event);
+akerr_ErrorContext AKERR_NOIGNORE *akgl_actor_cmhf_left_on(akgl_Actor *obj, SDL_Event *event);
 /**
  * @brief Stop the actor moving left, zeroing everything on the x axis.
  * @param obj   The actor to stop. Required. `basechar` is not needed here.
@@ -378,7 +378,7 @@ akerr_ErrorContext AKERR_NOIGNORE *akgl_Actor_cmhf_left_on(akgl_Actor *obj, SDL_
  * @note It clears the x axis whichever way the actor was going, so releasing
  *       left while holding right also stops the rightward movement.
  */
-akerr_ErrorContext AKERR_NOIGNORE *akgl_Actor_cmhf_left_off(akgl_Actor *obj, SDL_Event *event);
+akerr_ErrorContext AKERR_NOIGNORE *akgl_actor_cmhf_left_off(akgl_Actor *obj, SDL_Event *event);
 /**
  * @brief Start the actor moving right, and turn it to face right.
  * @param obj   The actor to move. Required, along with its `basechar`.
@@ -386,7 +386,7 @@ akerr_ErrorContext AKERR_NOIGNORE *akgl_Actor_cmhf_left_off(akgl_Actor *obj, SDL
  * @return `NULL` on success, otherwise an error context owned by the caller.
  * @throws AKERR_NULLPOINTER If @p obj, @p event, or `obj->basechar` is `NULL`.
  */
-akerr_ErrorContext AKERR_NOIGNORE *akgl_Actor_cmhf_right_on(akgl_Actor *obj, SDL_Event *event);
+akerr_ErrorContext AKERR_NOIGNORE *akgl_actor_cmhf_right_on(akgl_Actor *obj, SDL_Event *event);
 /**
  * @brief Stop the actor moving right, zeroing everything on the x axis.
  * @param obj   The actor to stop. Required.
@@ -394,7 +394,7 @@ akerr_ErrorContext AKERR_NOIGNORE *akgl_Actor_cmhf_right_on(akgl_Actor *obj, SDL
  * @return `NULL` on success, otherwise an error context owned by the caller.
  * @throws AKERR_NULLPOINTER If @p obj or @p event is `NULL`.
  */
-akerr_ErrorContext AKERR_NOIGNORE *akgl_Actor_cmhf_right_off(akgl_Actor *obj, SDL_Event *event);
+akerr_ErrorContext AKERR_NOIGNORE *akgl_actor_cmhf_right_off(akgl_Actor *obj, SDL_Event *event);
 /**
  * @brief Start the actor moving up the screen, and turn it to face up.
  * @param obj   The actor to move. Required, along with its `basechar`, whose y
@@ -403,7 +403,7 @@ akerr_ErrorContext AKERR_NOIGNORE *akgl_Actor_cmhf_right_off(akgl_Actor *obj, SD
  * @return `NULL` on success, otherwise an error context owned by the caller.
  * @throws AKERR_NULLPOINTER If @p obj, @p event, or `obj->basechar` is `NULL`.
  */
-akerr_ErrorContext AKERR_NOIGNORE *akgl_Actor_cmhf_up_on(akgl_Actor *obj, SDL_Event *event);
+akerr_ErrorContext AKERR_NOIGNORE *akgl_actor_cmhf_up_on(akgl_Actor *obj, SDL_Event *event);
 /**
  * @brief Stop the actor moving up, zeroing everything on the y axis.
  * @param obj   The actor to stop. Required.
@@ -413,7 +413,7 @@ akerr_ErrorContext AKERR_NOIGNORE *akgl_Actor_cmhf_up_on(akgl_Actor *obj, SDL_Ev
  * @note This also zeroes `ey`, so an actor under gravity has its accumulated
  *       fall cancelled by releasing a movement key.
  */
-akerr_ErrorContext AKERR_NOIGNORE *akgl_Actor_cmhf_up_off(akgl_Actor *obj, SDL_Event *event);
+akerr_ErrorContext AKERR_NOIGNORE *akgl_actor_cmhf_up_off(akgl_Actor *obj, SDL_Event *event);
 /**
  * @brief Start the actor moving down the screen, and turn it to face down.
  * @param obj   The actor to move. Required, along with its `basechar`.
@@ -421,16 +421,16 @@ akerr_ErrorContext AKERR_NOIGNORE *akgl_Actor_cmhf_up_off(akgl_Actor *obj, SDL_E
  * @return `NULL` on success, otherwise an error context owned by the caller.
  * @throws AKERR_NULLPOINTER If @p obj, @p event, or `obj->basechar` is `NULL`.
  */
-akerr_ErrorContext AKERR_NOIGNORE *akgl_Actor_cmhf_down_on(akgl_Actor *obj, SDL_Event *event);
+akerr_ErrorContext AKERR_NOIGNORE *akgl_actor_cmhf_down_on(akgl_Actor *obj, SDL_Event *event);
 /**
  * @brief Stop the actor moving down, zeroing everything on the y axis.
  * @param obj   The actor to stop. Required.
  * @param event The event that triggered this. Required, but not read.
  * @return `NULL` on success, otherwise an error context owned by the caller.
  * @throws AKERR_NULLPOINTER If @p obj or @p event is `NULL`.
- * @note Zeroes `ey` as well; see akgl_Actor_cmhf_up_off.
+ * @note Zeroes `ey` as well; see akgl_actor_cmhf_up_off.
  */
-akerr_ErrorContext AKERR_NOIGNORE *akgl_Actor_cmhf_down_off(akgl_Actor *obj, SDL_Event *event);
+akerr_ErrorContext AKERR_NOIGNORE *akgl_actor_cmhf_down_off(akgl_Actor *obj, SDL_Event *event);
 
 /**
  * @brief `SDL_EnumerateProperties` callback that applies an akgl_Iterator to one registered actor.