binding-tier-1: Lua 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/lua/.

Detachability contract for the Lua binding

• bindings/lua/ — proven/ (sources), spec/ (busted tests),
  *.rockspec, Justfile, symbol-manifest.txt
• bindings/c/include/proven.h — vendored on extraction
• .github/workflows/lua-ci.yml — workflow + sparse-checkout

Root Justfile gains lua-{check,build,test,clean} one-line
forwarders. The Lua binding consumes libproven via LuaJIT FFI
(ffi.cdef + ffi.load); the ffi.load path resolves
PROVEN_LIB_PATH at runtime so the test harness works without
LD_LIBRARY_PATH globals.

Replication

• chapel → lua
• *.chpl → *.lua
• Mason.toml → proven-*.rockspec (current files:
  proven-0.3.0-1.rockspec, proven-0.9.0-1.rockspec)
• chpl --version → lua -v (and luarocks --version)
• Chapel chpl --library typecheck → luac -p (parse-check) on each
  source module; Chapel smoke / tests → busted spec runs

WIRED subset starts at the proven#88 quintet. Land in a single PR
titled feat(lua-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