V3 step 3.5 — showcase8: the everything-tour (done 2026-09-20)

Suite 57/57 (26 run — incl. 3 trap-aborts — + 31 reject). Single-file proof that every lowered construct composes: showcase8.mod → ExitCode 170, hand-computed, first try.

Coverage (in execution order)

FOR-filled vector + indexed accumulation (arrays)
Nested matrix stores (multi-dim headers)
Set union + IN gate
String store + indexed CHAR compare
RECORD + nested WITH field updates
Subrange + alias use (zero net, for coverage)
INTEGER→REAL conversion, real arithmetic + comparison
CASE with ranges + ELSE
WHILE down-loop, REPEAT up-loop, LOOP/EXIT up-loop
Final boolean + char gate into ExitCode

Arithmetic (hand check)

100 (vector) + 6 (matrix) + 1 (IN) + 2 (char) + 42 (WITH fields)

7 (subrange) + 10 (real gate) + 1 (CASE) − 4 (WHILE) + 2 (REPEAT) + 3 (LOOP) = 170. Every intermediate asserted in the file comments; the binary agreed on the first run.

Notes

170 < 256 by design (exit codes are 8-bit); the tour stays clear of that ceiling deliberately.
WITH-on-field-designator and deep-copy paths from 3.4 both execute here (not just in their unit tests).
Next showcase point: 3.6 pointers (linked structures need NEW; currently impossible to build one).