Stop the listings and their chapters stating fixed defects as fact

You were right that this was still everywhere. The two `.bas` files carried
their workarounds as present-tense statements about the interpreter -- "a name
first created inside a GOSUB costs a value slot that is never handed back",
"writing PAST the terminator of a short row draws nothing at all", "SSHAPE and
GSHAPE ignore the subscript on a string array", "a FOR inside a BEGIN block does
not survive the RETURN" -- and every one of those is now false. A comment that
lies is worse than no comment, and these were the first thing anybody opening
the files would read.

**The characters game takes the geometry fix.** `CW# = 16` becomes `CW# =
RGR(3)`, and the grid comes from `RWINDOW`, so the game fits whatever window and
font the host gives it. That was the one thing in the listing that would break on
a different font, and `RGR(3)` and `RWINDOW` were added to the interpreter
because of it -- leaving the constant in place while Chapter 17 teaches the
function was the inconsistency worth closing. `RGR(1)` still comes first so a
build with no graphics device refuses by naming the device that is missing.

Everything else in both listings keeps its shape and says why. Declaring every
name up front, guarding loops with `GOTO`, six scalars for six brick stamps: none
is forced any more and none costs anything, so they stay, with the comments
marking which rules stand and which are history. The sprites header's five traps
are marked FIXED where they are fixed.

The chapters follow: Chapter 17 Step 2 no longer says "the listing still has
`CW# = 16`", and Chapter 18's trap section is "five things that did not do what
they looked like" with the two that still stand named up front rather than left
to be counted.

Verified: Chapter 17 Step 2's block is once again verbatim from the listing, so
every quoted fragment in both chapters matches its source with no exceptions;
both games run 40 seconds on the SDL frontend with no error line; both suites
green in both configurations; `docs_examples` and `docs_screenshots --check`
pass.

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

examples/breakout/sprites/breakout.bas

@@ -7,12 +7,18 @@ REM  Five things about this interpreter shape everything below, and they
 REM  are worth knowing before the first line stops making sense.
 REM
 REM  1. The text layer repaints every row of the window opaque black after
-REM     the program's steps have run, so anything DRAW or BOX put on the
-REM     screen is wiped before it is ever presented. Sprites are drawn
-REM     after the text layer, so a sprite is the only thing that can be
-REM     seen. Everything drawn here is therefore captured with SSHAPE and
-REM     installed as a sprite with SPRSAV -- that is what sprites 1 and 2
-REM     are. They are the screen.
+REM     the program's steps have run, so by default anything DRAW or BOX
+REM     put on the screen is wiped before it is ever presented. Sprites are
+REM     drawn after the text layer, so a sprite is the one thing that is
+REM     seen for nothing. Everything drawn here is therefore captured with
+REM     SSHAPE and installed as a sprite with SPRSAV -- that is what
+REM     sprites 1 and 2 are. They are the screen.
+REM
+REM     (WINDOW can shrink the text area and hand the rest of the window to
+REM     the drawing verbs; it could not be reached from this build when
+REM     this was written. It would not help here anyway: a drawing has to
+REM     be re-issued every frame and fit inside one batch, and a sprite has
+REM     neither constraint.)
 REM
 REM  2. The host runs 256 source lines and then presents the frame, and a
 REM     present throws the drawing buffer away. So all the drawing between
@@ -33,9 +39,10 @@ REM     enough to both that a constant is spelled out rather than named
 REM     and several routines that would read better as subroutines are
 REM     BEGIN blocks instead.
 REM
-REM  5. Five things in this dialect do not do what they look like they do,
-REM     and each one cost an evening. They are noted where they bite, and
-REM     collected here so nobody has to find them twice:
+REM  5. Five things in this dialect did not do what they looked like they
+REM     did, and each one cost an evening. THREE OF THEM HAVE SINCE BEEN
+REM     FIXED, and are marked below; the shape of this listing is still
+REM     theirs, which is why they are still written down:
 REM
 REM     * **The left operand decides whether an expression is done in
 REM       integers or in floats.** 0 - V% throws V%'s fraction away and
@@ -48,12 +55,16 @@ REM       result somewhere with a % on it.
 REM     * A FOR whose bounds are equal does not run its body at all, so
 REM       every loop over a list has the one-item case written out beside
 REM       it.
-REM     * A FOR inside a BEGIN block does not survive the RETURN of the
-REM       routine holding it; the interpreter loses the GOSUB. Loops in
-REM       this program are guarded by GOTO rather than wrapped in a block.
-REM     * SSHAPE and GSHAPE ignore the subscript on a string array, so
-REM       every element resolves to element zero. The six brick stamps are
-REM       therefore six separate scalars.
+REM     * FIXED. A FOR inside a BEGIN block that was SKIPPED did not
+REM       survive the RETURN of the routine holding it; the interpreter
+REM       lost the GOSUB and reported "RETURN outside the context of
+REM       GOSUB". Loops in this program are guarded by GOTO rather than
+REM       wrapped in a block, and are left that way because it costs
+REM       nothing. TODO.md section 9 item 2.
+REM     * FIXED. SSHAPE and GSHAPE ignored the subscript on a string array,
+REM       so every element resolved to element zero. The six brick stamps
+REM       are six separate scalars for that reason; an array works now.
+REM       TODO.md section 9 item 6.
 REM     * READ walks one cursor through every DATA item in the file in the
 REM       order they were written, no matter which routine is reading.
 REM
@@ -140,10 +151,11 @@ REM ------------------------------------------------------- shapes and dirt
 REM SHN# counts the SSHAPE slots spent. There are sixteen, nothing gives
 REM one back, and GRAPHIC 5 gives back all of them at once -- so the brick
 REM stamps are thrown away and rebuilt every time the pool runs dry.
-REM One scalar per row colour, and scalars rather than an array on
-REM purpose: SSHAPE and GSHAPE read the leaf they are handed without
-REM applying its subscript, so a string array element always resolves to
-REM element zero and every brick comes out the same colour.
+REM One scalar per row colour, and scalars rather than an array because
+REM SSHAPE and GSHAPE used to read the leaf they were handed without
+REM applying its subscript -- a string array element always resolved to
+REM element zero, and every brick came out the same colour. That is fixed
+REM and an array would work now; six scalars is what this listing has.
 S0$ = ""
 S1$ = ""
 S2$ = ""
@@ -330,9 +342,10 @@ REM
 REM  Rebuilding the brick stamps comes first, because everything else
 REM  draws with them and GRAPHIC 5 has just thrown them away.
 REM =====================================================================
-REM Labels rather than BEGIN blocks here, and it is not a style choice: a
-REM RETURN inside a block leaves the interpreter with no GOSUB to return
-REM from and stops the program.
+REM Labels rather than BEGIN blocks here. When this was written it was not
+REM a style choice -- a loop inside a block that was skipped left the
+REM interpreter with no GOSUB to return from and stopped the program. That
+REM is fixed; the shape is kept because it reads the same either way.
 LABEL DRAWJOB
 IF SHN# < 14 THEN GOTO DRAWJOB2
 GOSUB DRAWPROTOS
@@ -399,8 +412,9 @@ Z$ = S2$ : T1# = RS#(2) : T2# = RC#(2) : GOSUB STAMPROW
 Z$ = S3$ : T1# = RS#(3) : T2# = RC#(3) : GOSUB STAMPROW
 Z$ = S4$ : T1# = RS#(4) : T2# = RC#(4) : GOSUB STAMPROW
 Z$ = S5$ : T1# = RS#(5) : T2# = RC#(5) : GOSUB STAMPROW
-REM A FOR inside a BEGIN block does not survive the RETURN at the end of
-REM the routine that holds it, so this loop is guarded by a GOTO instead.
+REM A skipped BEGIN block holding a FOR used to break the RETURN at the end
+REM of the routine holding it, so this loop is guarded by a GOTO instead.
+REM Fixed since; left alone because a GOTO guard costs nothing.
 IF PN# = 1 THEN DRAW PC#(0), PX1#(0), PY1#(0) TO PX2#(0), PY2#(0)
 IF PN# < 2 THEN GOTO PLDONE
 FOR I# = 0 TO PN# - 1