Check the reference corpus in, so the build stops needing the Go submodule

All 41 .bas/.txt pairs copied byte for byte from basicinterpreter@d76162c into
tests/reference/, plus the Commodore font into assets/fonts/ -- the two things
that tied the build to deps/basicinterpret. Both were verified cmp-identical
to the submodule copies.

This reverses a decision that was deliberate and correct at the time: the
corpus was driven in place because copying a submodule's corpus guarantees
drift. Overruled on purpose -- the Go dependency is being deprecated, and a
build that cannot run its acceptance suite without cloning the implementation
it replaced is not finished. tests/reference/README.md records what the drift
now costs and that those expectations are never edited.

Checked rather than assumed: both configurations configure, build and pass
from scratch with deps/basicinterpret moved out of the tree entirely.

The submodule is kept as the behavioural spec, which is a real use. The font
came with an open licence question; assets/fonts/PROVENANCE.md states it.

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

tests/reference/language/flowcontrol/forloop.bas

@@ -0,0 +1,4 @@
+10 FOR I# = 1 TO 4
+20 PRINT I#
+30 NEXT I#
+40 QUIT

tests/reference/language/flowcontrol/forloop.txt

@@ -0,0 +1,4 @@
+1
+2
+3
+4

tests/reference/language/flowcontrol/forloopwaitingforcommand.bas

@@ -0,0 +1,13 @@
+10 REM This shows the waitingForCommand utility in the BasicEnvironment
+11 REM We have a FOR loop here with a condition where the loop should
+12 REM not execute at all. But because the checking of the conditional is
+13 REM delayed until the bottom of the loop, we run the risk of the
+14 REM runtime executing every line between FOR ... NEXT even though it
+15 REM shouldn't. waitingForCommand prevents this from occurring
+20 FOR I# = 1 TO 1
+30 PRINT "waitingForCommand FAILS if this is seen"
+40 NEXT I#
+50 FOR I# = 1 TO 2
+60 PRINT "waitingForCommand PASS if this is seen"
+70 NEXT I#
+80 QUIT

tests/reference/language/flowcontrol/forloopwaitingforcommand.txt

@@ -0,0 +1,2 @@
+waitingForCommand PASS if this is seen
+waitingForCommand PASS if this is seen

tests/reference/language/flowcontrol/goto.bas

@@ -0,0 +1,3 @@
+10 GOTO 30
+20 PRINT "FAILURE"
+30 PRINT "SUCCESS"

tests/reference/language/flowcontrol/goto.txt

@@ -0,0 +1 @@
+SUCCESS

tests/reference/language/flowcontrol/ifthenelse.bas

@@ -0,0 +1,11 @@
+10 A# = 1
+20 IF A# == 1 THEN GOTO 30 ELSE GOTO 40
+30 PRINT "A# IS 1"
+35 GOTO 50
+45 PRINT "A# IS NOT 1"
+50 IF A# == 2 THEN GOTO 60 ELSE GOTO 80
+60 PRINT "A# IS 2"
+65 PRINT A#
+70 GOTO 90
+80 PRINT "A# IS NOT 2"
+90 PRINT "DONE"

tests/reference/language/flowcontrol/ifthenelse.txt

@@ -0,0 +1,3 @@
+A# IS 1
+A# IS NOT 2
+DONE

tests/reference/language/flowcontrol/nestedforloops.bas

@@ -0,0 +1,10 @@
+10 FOR I# = 1 TO 4
+15     PRINT "OUTER : I# IS " + I#
+20         FOR J# = 2 TO 3
+23             PRINT "INNER : I# IS " + I#
+25             PRINT "INNER : J# IS " + J#
+30             PRINT "INNER : I# * J# IS " + (I# * J#)
+40         NEXT J#
+50     NEXT I#
+60 PRINT "DONE"
+70 QUIT

tests/reference/language/flowcontrol/nestedforloops.txt

@@ -0,0 +1,29 @@
+OUTER : I# IS 1
+INNER : I# IS 1
+INNER : J# IS 2
+INNER : I# * J# IS 2
+INNER : I# IS 1
+INNER : J# IS 3
+INNER : I# * J# IS 3
+OUTER : I# IS 2
+INNER : I# IS 2
+INNER : J# IS 2
+INNER : I# * J# IS 4
+INNER : I# IS 2
+INNER : J# IS 3
+INNER : I# * J# IS 6
+OUTER : I# IS 3
+INNER : I# IS 3
+INNER : J# IS 2
+INNER : I# * J# IS 6
+INNER : I# IS 3
+INNER : J# IS 3
+INNER : I# * J# IS 9
+OUTER : I# IS 4
+INNER : I# IS 4
+INNER : J# IS 2
+INNER : I# * J# IS 8
+INNER : I# IS 4
+INNER : J# IS 3
+INNER : I# * J# IS 12
+DONE

tests/reference/language/flowcontrol/nestedforloopwaitingforcommand.bas

@@ -0,0 +1,11 @@
+10 REM This shows the waitingForCommand utility in the BasicEnvironment
+11 REM when we have a nested for loop. The inner loop SHOULD execute, but
+12 REM the outer loop should NOT execute. Therefore, neither loop should execute.
+20 FOR I# = 1 TO 0
+25 FOR J# = 2 TO 4
+30 PRINT "waitingForCommand FAILS if this is seen"
+32 QUIT
+35 NEXT J#
+40 NEXT I#
+50 PRINT "SUCCESS"
+80 QUIT

tests/reference/language/flowcontrol/nestedforloopwaitingforcommand.txt

@@ -0,0 +1 @@
+SUCCESS