Close out the collision conversion in TODO.md

§6 item 39 is done: both listings and both tutorials are on SOLID,
COLLISION 2 and RCOLLISION. Record the two traps the conversion turned up
that no error reports -- BUMP's mask is by sprite number, so the artwork
game's balls are bits 16, 32 and 64; and a bare SOLID after the fill loop
retires the rectangles it was meant to precede.

§6 item 38 and §9 item 9 carried statements the work since made false.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EwxGB6TdoVvZ11KQQME9cL

TODO.md

@@ -2244,35 +2244,35 @@ each is here so the reasoning does not have to be reconstructed.
     naive all-pairs sweep at 0.7% of a frame at 64 actors and 11% at 256, so the crossover is
     well above anything a Commodore-shaped sprite budget will reach.
 
-    Also still open at the seam: the contact is computed and discarded. §6 item 40 and the
-    BASIC surface built on it are what consume it.
+    What remains is only the pairing seam above. The contact itself is consumed:
+    `akbasic_collision_service()` pulls it per sprite and the `RCOLLISION` fields are what both
+    breakout games now bounce on.
 
-39. **Convert the breakout listings and chapters 17 and 18 to the collision verbs.** This is the
-    payoff, and it is deliberately not part of the integration commit.
+39. ~~**Convert the breakout listings and chapters 17 and 18 to the collision verbs.**~~
+    **Done.** Both games and both tutorials now register their bricks with `SOLID`, arm
+    `COLLISION 2` and read the contact back with `RCOLLISION`.
 
-    Neither game calls `COLLISION` or `BUMP` even once today. Of roughly 230 lines of collision
-    code across the two, about 19 are sprite-against-sprite; the rest is a sprite against
-    numbers in a BASIC array or against bare constants, because bricks are text characters in
-    one game and stamped pixels inside one big sprite in the other. Static collision geometry is
-    what changes that — a brick becomes a collidable box without spending a sprite slot.
+    What went: `BALLBRICKS` (29 lines) and `TESTCELL` (28) in the artwork game, and `HITTEST`
+    (14) plus its pixel-to-cell arithmetic in the characters game — replaced by a handler that
+    asks which box was hit and which axis to reverse. The hand-written minimum-translation-axis
+    is `RCOLLISION(n, 7)`. `BUILDLIVE`/`BUILDROW`/`STAMPROW` went with the full-field redraw
+    they existed to make cheap, and the artwork game gave six orphaned declarations back with
+    them: the label table went from 61 of 64 to 57.
 
-    What goes, concretely:
+    Two things are worth keeping from doing it, because neither is obvious and both cost an
+    evening:
 
-    - `examples/breakout/sprites/breakout.bas` — `BALLBRICKS` (29 lines) and `TESTCELL` (28)
-      become a handler that reads which box was hit and which axis to reverse. The
-      hand-written minimum-translation-axis at `:661-666` is a contact field. `BUILDLIVE` and
-      `BUILDROW` stop maintaining a parallel `BRK#()` grid.
-    - `examples/breakout/characters/breakout.bas` — `HITTEST` (14 lines) and the pixel-to-cell
-      arithmetic go the same way, and `PADHIT`'s five-line overlap test becomes `BUMP`.
+    - **`BUMP`'s mask is by sprite number, not by anything the handler is about.** The artwork
+      game's balls are sprites 5, 6 and 7, so their bits are 16, 32 and 64. A handler that
+      tests 1, 2 and 4 runs, matches nothing and returns, with no error and nothing to see.
+    - **A bare `SOLID` must run *before* the level is laid out, not after.** Put after the fill
+      loop it retires all sixty rectangles that were just registered, and the only symptom is a
+      ball that passes through the wall.
 
-    **The documentation cost is the reason this is separate.** Chapter 17 Step 10 and chapter 18
-    Steps 9 and 13 are built around that arithmetic, both chapters' examples are executed by
-    `docs_examples`, and both were rewritten and validated immediately before this work started.
-    Folding a listing rewrite into a library integration would make neither reviewable.
-
-    Sequence it after §9 item 9 if that is ever fixed, since a game that no longer spends two
-    sprites on the screen has two more to spend on collidable things, and the two rewrites would
-    otherwise touch the same lines twice.
+    Chapter 18 also lost a rule it depended on and no longer stated: a `FOR` with equal bounds
+    does not run its body (§6 item 19), which is why every list in the chapter has its one-item
+    case written out beside the loop. It is now stated in Step 7 where it is first used, rather
+    than cross-referenced to a step that the rewrite deleted.
 
 40. **`akbasic_runtime_call_function()`: call a BASIC function from C with bound values.**
 
@@ -3151,7 +3151,8 @@ reduced against `build/basic`, the stdio build, unless it says otherwise.
 
 9. ~~**A program that wants a picture on the screen has to spend a sprite slot on it, and
    `examples/breakout/sprites/breakout.bas` spends two of its eight on the screen itself.**~~
-   **Done for the interpreter; the listing has not been converted yet -- that is §6 item 39.**
+   **Done.** The listing has been converted with it: no `SSHAPE` of the screen, no `PACE`
+   routine hunting for a batch boundary, and both slots free.
 
    The drawing verbs now render into a layer the frame composites under the text and the
    sprites (`akbasic_graphics_akgl_begin`/`_end`/`_render`, `src/graphics_akgl.c`), so a