fuzz: Int→Bool predicate generation; silence point-free appendTR false-alarm

[emeryberger]

Two follow-ups from the campaign wrap-up.

Int → Bool predicate generation

Generalizes the Char → Bool predicate machinery to any α → Bool predicate, adding Int → Bool. A predicate value is a finite subset of a fixed element universe (chars from the alphabet, or a small signed-Int range) — "is this element in the subset?" — which has identical semantics in a Lean and a Python lambda and is serializable. The tag now records the element type ({"__pred__": [...], "ety": "Char"|"Int"}) so the Lean literal and Python materialize rebuild the right membership test.

Unlocks Cedar's setAll/setAny/setFilter (harvest 535 → 538); all three differentially agree with the oracle. Regression case (18) added.

Silence point-free appendTR self-coverage false-alarm

Point-free List.append/appendTR/binop are now handled before the fallthrough.* self-coverage tag (marking const.* instead), so the report no longer falsely flags List.appendTR as a possibly-broken core handler. The emitted code is unchanged and correct ((lambda a, b: a + b)); this only fixes the reporting.

Verification

• RegressionFixes (44 cases), Comprehensions, TailCalls green; lake build + lake build Corpus green.
• Local corpus sweep clean (0 bugs), no fallthrough warning.
• Char→Bool predicates still work (rust-lean-models contains_char_filter/find_char_filter verified).