Fix Doxygen gate failures on main

Four independent defects that made 'doxygen Doxyfile' exit 1:

- runtime.h: a stacked doc block above akbasic_runtime_new_function
  was left directly above akbasic_runtime_call_function's declaration
  with no function in between, so Doxygen glommed both blocks onto
  call_function and duplicated the @param obj/@param dest entries.
  Moved the block back to sit directly above new_function.
- sprite.h/akgl.h/sprite_akgl.c: three #AKGL_*/#AKBASIC_SHAPE_* Doxygen
  autolinks pointed at libakgl symbols outside this Doxyfile's INPUT,
  so they could never resolve. Converted them to plain code spans.
- scanner.c: peek(), peek_next() and match_next_char() were each
  missing @param obj (and match_next_char also cm/truetype/falsetype).
  Filled in the missing entries.
- Doxyfile: the error.h include graph hit DOT_GRAPH_MAX_NODES at
  exactly the default of 50. Raised it to 100.

Verified 'doxygen Doxyfile' now exits 0 with graphviz installed.

Refs #56

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

include/akbasic/akgl.h

@@ -296,7 +296,7 @@ typedef struct
      *
      * Claimed up front rather than per scan for two reasons. The pool is shared
      * with whatever host this interpreter is embedded in -- a game with its own
-     * shaped actors draws from the same #AKGL_MAX_HEAP_COLLISION_PROXY -- so
+     * shaped actors draws from the same `AKGL_MAX_HEAP_COLLISION_PROXY` -- so
      * running out is a real possibility, and it should be an init-time failure
      * naming the pool rather than a collision scan that starts refusing halfway
      * through a game. And a proxy carries a *copy* of its shape, so there is

include/akbasic/runtime.h

@@ -832,13 +832,6 @@ akerr_ErrorContext AKERR_NOIGNORE *akbasic_runtime_reserve_globals(akbasic_Runti
  * @throws AKBASIC_ERR_BOUNDS When every variable slot is in use.
  */
 akerr_ErrorContext AKERR_NOIGNORE *akbasic_runtime_new_variable(akbasic_Runtime *obj, akbasic_Variable **dest);
-/**
- * @brief Take an unused function definition from the runtime's pool.
- * @param obj Object to initialize, inspect, or modify.
- * @param dest Output destination populated by the function.
- * @return `NULL` on success, otherwise an error context owned by the caller.
- * @throws AKBASIC_ERR_BOUNDS When every function slot is in use.
- */
 /**
  * @brief Call a user-defined function with values a caller already has.
  *
@@ -865,6 +858,13 @@ akerr_ErrorContext AKERR_NOIGNORE *akbasic_runtime_new_variable(akbasic_Runtime
  */
 akerr_ErrorContext AKERR_NOIGNORE *akbasic_runtime_call_function(struct akbasic_Runtime *obj, const char *name, akbasic_Value **args, int nargs, akbasic_Value **dest);
 
+/**
+ * @brief Take an unused function definition from the runtime's pool.
+ * @param obj Object to initialize, inspect, or modify.
+ * @param dest Output destination populated by the function.
+ * @return `NULL` on success, otherwise an error context owned by the caller.
+ * @throws AKBASIC_ERR_BOUNDS When every function slot is in use.
+ */
 akerr_ErrorContext AKERR_NOIGNORE *akbasic_runtime_new_function(akbasic_Runtime *obj, akbasic_FunctionDef **dest);
 /**
  * @brief File one already-scanned source line under its line number.

include/akbasic/sprite.h

@@ -59,7 +59,7 @@
  * with headroom. The ceiling matters because these come out of libakgl's
  * collision proxy pool, which is shared with whatever host this interpreter is
  * embedded in: eight sprites plus sixty-four solids is seventy-two of
- * #AKGL_MAX_HEAP_COLLISION_PROXY, and the rest is the host's.
+ * `AKGL_MAX_HEAP_COLLISION_PROXY`, and the rest is the host's.
  */
 #ifndef AKBASIC_MAX_SOLIDS
 #define AKBASIC_MAX_SOLIDS		64
@@ -117,7 +117,7 @@ typedef struct
     int speed;			/*   clockwise from vertical, and 0-15		*/
 
     /**
-     * SPRHIT's collision shape: one of the #AKBASIC_SHAPE_* kinds, and a
+     * SPRHIT's collision shape: one of the `AKBASIC_SHAPE_*` kinds, and a
      * rectangle measured from the sprite's top-left corner.
      *
      * `shapeexplicit` is what separates "the program asked for the whole frame"