pasmith: fuzz the {$Q+}/{$R+} check machinery

• Type: feature (fuzz grammar — Track T owns the tool).
• Opened: 2026-07-15, after the night that landed both features ([[feature-pascal-overflow-checks-q-plus]] slices all-hosted-targets, [[feature-pascal-range-checks-r-plus]] slices 1-5).

Why

The checks were hand-oracle-verified shape by shape, and TWICE the ticket's assumed semantics were wrong until probed (FPC does NOT check Abs/Sqr or subword ops). A generator that sprinkles {$Q+}/{$R+}/{$Q-}/{$R-} regions over its existing arithmetic/array/subrange rungs and counts caught EIntOverflow/ERangeError per checkpoint would differentially pin the whole semantic surface against FPC — including the statement-anchor timing rule (trange4) that a directive between RHS and statement end must not retro-apply.

Sketch

• New knob --checks N: with probability derived from N, wrap a statement run in {$Q+}/{$R+} (and matching try/except counting per class).
• The checksum mixes the caught-counts, so a divergence localizes like any other checkpoint.
• Needs pasmith's exception rung (already exists: --excepts).