binding-tier-1: OCaml binding standup (replicate from Chapel pilot)

[hyperpolymath]

Parent: #129.

Scope

Apply the detachable-harness template from
docs/adr/0001-binding-ci-template.adoc to bindings/ocaml/.

Detachability contract for the OCaml binding

• bindings/ocaml/ — lib/, test/, dune-project, *.opam,
  Justfile, symbol-manifest.txt
• bindings/c/include/proven.h — vendored on extraction (the binding
  references it via %{env_or:PROVEN_INCLUDE_PATH=...})
• .github/workflows/ocaml-ci.yml — workflow + sparse-checkout

Root Justfile gains ocaml-{check,build,test,clean} one-line
forwarders.

Replication

• chapel → ocaml
• *.chpl → *.ml / *.mli
• Mason.toml → dune-project (+ *.opam)
• chpl --version → ocaml --version (or dune --version)
• Chapel chpl --library → dune build / dune build --only-packages proven

The binding uses ctypes / dune for FFI; the (c_library_flags ...) /
(c_library_deps ...) clauses consume PROVEN_LIB_PATH /
PROVEN_INCLUDE_PATH via env, NOT via hardcoded ../../ffi/zig/...
paths.

WIRED subset starts at the proven#88 quintet. Land in a single PR
titled feat(ocaml-binding): stand up detachable CI + tests — binding-tier-1.

References

• Parent: proven: binding-tier-1 detachable-harness template — Chapel pilot + replication #129
• Pilot ADR: docs/adr/0002-chapel-binding-standup.adoc
• Template ADR: docs/adr/0001-binding-ci-template.adoc