ocaml: make property-coverage references a call-graph closure

[subsetpark]

Problem

The core-coverage rule ("property tests must reference every decision API") harvested references only from the QCheck2.Test.make callback. So an API exercised through the generator (gen_graph building inputs via add_dependency) or through a higher-order test helper (totality (fun s -> Core.parse s)) was invisible — a recurring false-negative we kept patching per-case.

Fix — uniform, obligatory call-graph closure

Rather than harvest at one syntactic site, expansion now follows the call graph:

1. All top-level bindings join the graph, not just functions — so a bound generator's references expand transitively.
2. A property check harvests every argument (callback and generator), expanded through the graph.
3. A binding that reaches a meaningful-property-bearing binding through the graph (e.g. a property produced by a higher-order helper) contributes its references to coverage.

The meaningfulness gate is preserved: a linking property over unit that only ignores a surface still doesn't count.

Why syntactic (not semantic)

The remaining hard case after this — a property selected at runtime from a data structure — is genuine dynamic dispatch, which semantic (typed-tree) resolution also wouldn't solve (it's flow, not name resolution; see #6). Call-graph closure is the right tool for reachability and is semantic-independent.

Tests (ocaml/test.sh)

• New closure fixture: a core whose three decision APIs are reached directly, via a generator, and via a higher-order helper — all must count (no violation).
• Regression: a linking-only unit property that ignores the API must still fail coverage.
• Full OCaml suite passes; onton stays at 0 violations.

🤖 Generated with Claude Code

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