Remove the corner helpers akgl_collide_rectangles no longer uses

akgl_rectangle_points, akgl_collide_point_rectangle, akgl_Point and
akgl_RectanglePoints go. They were the intermediate form of an implementation
that changed: akgl_collide_rectangles was eight corner-containment tests built on
them, and it has been four span comparisons since the cross-case fix. Nothing
outside tests/ called either function, and a point-in-rectangle test is four
comparisons a caller can write without a struct conversion in front of them.

akgl_collide_rectangles stays. It has two correct callers in the sidescroller
asking a game-level overlap question -- a coin, a hazard, from an updatefunc --
where a bool is the whole answer and a proxy plus a narrowphase call would be
computing a normal nothing reads. TODO.md records the split rather than leaving
it to be rediscovered.

Public API removal, so 194 exported akgl_ symbols against 196, and the manual's
counts move with them. The perf suite loses its rectangle_points row; the
all-pairs sweep stays as the control it is now labelled, and PERFORMANCE.md says
what 0.8.0 measured against it -- 188.5 us for 32,640 pairs at 256 actors, where
a whole step with collision attached is 54.1 us doing strictly more.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KzBDV2fqgnUAcqCKqKvc71

TODO.md

@@ -2518,36 +2518,36 @@ follow that are true today and would not survive a change:
 
 `akgl_ccd_arena_highwater()` is public so a game can assert its own ceiling.
 
-## The `util.h` rectangle helpers stay, and why
+## `akgl_collide_rectangles` stays; the corner helpers did not
 
 The collision plan's last step was to **delete `akgl_rectangle_points`,
 `akgl_collide_point_rectangle` and `akgl_collide_rectangles`** once the shape API
-landed, on the grounds that collision now has a real narrowphase. That step was
-not taken, and this is the reasoning rather than an oversight.
+landed, on the grounds that collision now has a real narrowphase. Two of the
+three went, in 0.8.0, along with `akgl_Point` and `akgl_RectanglePoints`. The
+third stays, and this is the reasoning rather than an oversight.
 
-- **They still have callers that are correct.** `examples/sidescroller/player.c`
-  uses `akgl_collide_rectangles` twice, for coins and for hazards. Those are
-  overlap *questions* asked from an `updatefunc` -- "am I touching this" -- and
-  the right answer is a `bool`. Routing them through a collision shape would
-  mean a proxy, a broad-phase insert and a narrowphase call to compute a normal
-  and a depth that nothing reads.
-- **`akgl_collide_rectangles` was fixed in this same series**, not left broken.
-  It was a corner test that missed the cross case and truncated through
-  `akgl_Point`'s `int` members; it is a span test now, exact in `float32_t`.
-  Deleting it two commits after fixing it is a strange thing to do to a caller.
+**Why the two went.** They were the intermediate form of an implementation that
+changed. `akgl_collide_rectangles` was eight corner-containment tests built on
+them; it is four span comparisons now and does not go through either. Nothing
+outside `tests/` called them, and a point-in-rectangle test is four comparisons a
+caller can write without a struct conversion in front of it.
+
+**Why the third stays.**
+
+- **It has callers that are correct.** `examples/sidescroller/player.c` uses it
+  twice, for coins and for hazards. Those are overlap *questions* asked from an
+  `updatefunc` -- "am I touching this" -- and the right answer is a `bool`.
+  Routing them through a collision shape would mean a proxy, a broad-phase insert
+  and a narrowphase call to compute a normal and a depth that nothing reads.
+- **It was fixed in this same series**, not left broken. It missed the cross case
+  and truncated through `akgl_Point`'s `int` members; it is exact in `float32_t`
+  now. Deleting it two commits after fixing it is a strange thing to do to a
+  caller.
 - **A game-level overlap question is not always a physics question.** A minimap
   marker, a UI hit test, "is the cursor over this". None of those wants to be
   pushed, and none of them belongs in a collision world.
 
-`akgl_rectangle_points` and `akgl_collide_point_rectangle` are the weaker case:
-nothing outside `tests/` calls either, and `akgl_collide_rectangles` no longer
-does since it stopped working corner by corner. They are kept for symmetry with
-the one that is used and because a point-in-rectangle test is the other half of
-the same question -- but if a 0.9.0 wants to trim the public surface, those two
-are the candidates, not `akgl_collide_rectangles`.
-
-One thing found while writing this and fixed rather than recorded:
+One thing found while doing this and fixed rather than recorded:
 `akgl_RectanglePoints`' Doxygen comment still said `akgl_collide_rectangles`
 "works corner by corner rather than by comparing edge spans", which had been
-false since the fix. [Chapter 19](docs/19-utilities.md) already described the
-current behaviour correctly, so the header was the only place saying otherwise.
+false since the fix. It went with the type.