apl: :Trap exception machinery — Phase 7 complete (+5 tests, 450/450)

apl-throw raises a tagged ("apl-error" code msg) error.
apl-trap-matches? checks if codes list contains the error's code
(0 = catch-all, à la Dyalog).

Eval-stmt :trap clause wraps try-block with R7RS guard;
on match, runs catch-block; on mismatch, re-raises.
Bonus :throw AST node for testing.

test.sh + conformance.sh now load lib/r7rs.sx (for guard) and
include eval-ops + pipeline suites in scoreboard.

All Phase 7 unchecked items are now ticked.
Final scoreboard: 450/450 across 10 suites.

lib/apl/test.sh

@@ -18,6 +18,7 @@ TMPFILE=$(mktemp); trap "rm -f $TMPFILE" EXIT
 cat > "$TMPFILE" << 'EPOCHS'
 (epoch 1)
 (load "spec/stdlib.sx")
+(load "lib/r7rs.sx")
 (load "lib/apl/runtime.sx")
 (load "lib/apl/tokenizer.sx")
 (load "lib/apl/parser.sx")