Stop the artwork breakout drawing its screen into two sprites

It captured the HUD strip into sprite 1 and the whole play field into sprite 2,
and its own header called them "the screen". That was never a choice: a drawing
lasted one frame, so a sprite was the only thing the interpreter would redraw for
nothing. Both slots are free now, and five things went with them.

**`WINDOW 0, 35, 49, 36` is the first executable line.** The text layer repaints
every row it owns and by default owns the whole window; moved to two rows at the
bottom, it leaves the other thirty-five to the drawing verbs, and what the
program draws stays.

**`PACE` is gone.** It spun on `TI#` until a batch boundary so an `SSHAPE`
capture would not be cut in half by a present. Nothing is captured, so a drawing
spanning two batches simply arrives over two frames and the layer keeps both
halves. The 256-line drawing deadline that shaped every draw routine in this
listing does not apply to it any more.

**The flattened live list is gone** -- `BUILDLIVE`, `BUILDROW`, `STAMPROW` and
the four arrays behind them. They existed so a full-field redraw could be one
stamp and an advance per brick, and a full-field redraw existed because removing
one brick meant rebuilding all sixty. A broken brick is now erased in place with
a blank stamp, so the field is drawn once per level and not again.

**`BALLBRICKS` and `TESTCELL` are gone** -- about sixty lines that turned the
ball's box into a range of candidate cells, walked them with a nested `DO`, and
computed an overlap rectangle to pick an axis. `SOLID` registers each brick as
the level is laid out, `COLLISION 2` fires, and `RCOLLISION` says which brick,
which way out, how far, and which axis to reverse.

**The `SSHAPE` pool accounting is gone.** `SHN#` counted slots because every
frame's capture spent another and `GRAPHIC 5` had to throw them all away
periodically; eight are now spent once and never again.

Three mistakes worth recording, because each was silent:

- **The bricks were registered and then immediately thrown away.**
  `GOSUB BUILDLIVE` sat *after* the fill loop in `SETUPLEVEL` and meant "rebuild
  the list of what is standing"; replaced in place by a bare `SOLID`, it meant
  "retire everything" and ran after all sixty had been registered. Nothing
  failed -- the ball simply passed through the wall.
- **The handler tested the wrong bits.** `BUMP` is a mask by *sprite*, and the
  balls are sprites 5, 6 and 7, so their bits are 16, 32 and 64. Testing 1, 2 and
  4 asked about the HUD and field sprites that no longer exist.
- **The eraser stamps were undeclared**, so `SSHAPE` filled them inside
  `DRAWPROTOS` and they were empty everywhere else -- exactly the scope trap
  chapter 17 Step 3 is about, found by printing the handle inside the routine and
  again outside it.

Verified by driving it: a copy with a tracking paddle and auto-relaunch breaks
thirteen bricks in sixty seconds with no error line, and the shipped listing runs
clean. Both suites green.

Chapter 18 still describes the architecture this commit removed; that is the rest
of section 6 item 39.

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

examples/breakout/sprites/README.md

@@ -2,11 +2,11 @@
 
 Breakout, written entirely in BASIC for the AKGL BASIC interpreter, using downloaded CC0
 sprite artwork for the paddles, the balls and the powerup gems. The bricks, the HUD and
-the lettering are drawn, captured with `SSHAPE` and installed as sprites — because a
-sprite is the one thing this interpreter puts on the screen for nothing. The text layer
-owns every row of the window unless a program takes some back with `WINDOW`, and even
-then a drawing has to be re-issued every frame; a sprite is drawn from state the
-interpreter keeps.
+the lettering are drawn — `WINDOW` moves the text layer to two rows at the bottom, and
+everything the program draws then stays on the screen without being redrawn or captured.
+
+The bricks are also **collidable without being sprites**: `SOLID` registers a rectangle
+the interpreter collides against, so sixty of them cost none of the eight slots.
 
 ```sh
 ../../../build-akgl/basic breakout.bas