chore: port the ABI-FFI gate from Python to Julia (RSR-H4: no Python)

[hyperpolymath]

Summary

Clears the one pre-existing red on the estate's governance / Language / package anti-pattern policy check. scripts/abi-ffi-gate.py was the repo's last Python file (RSR-H4 bans Python — Julia for scripts/data, Rust for systems), and the whole-tree scanner flags it. Rather than suppress the scanner, this ports the gate to Julia and removes the .py, so the check goes green and the ABI↔FFI conformance gate keeps doing its job.

(Follow-up to #173 — this is the cleanup of the lone pre-existing failure carried on #172/#173.)

Changes

• scripts/abi-ffi-gate.jl (new) — a 1:1 Julia port of the former Python gate (Julia PCRE maps directly onto Python re). Same three checks, same messages, same exit codes:
  1. the Zig FFI carries no unrendered {{...}} template tokens;
  2. every %foreign "C:<name>" symbol in the ABI .idr sources is export fn-ed by the Zig FFI;
  3. the Idris resultToInt map and the Zig Result = enum(c_int) agree on names and values (Error/err unified).
• .github/workflows/abi-ffi-gate.yml — the ABI ↔ FFI structural conformance job now installs the pinned Julia 1.11.5 release tarball (mirroring the adjacent zig-build job's pinned-tarball pattern) and runs julia scripts/abi-ffi-gate.jl.
• scripts/abi-ffi-gate.py (removed) — the last Python file in the repo.

RSR Quality Checklist

Required

• Tests pass — gate runs clean locally (julia 1.11.5); cargo/Zig/Idris surfaces untouched
• Code is formatted — idiomatic Julia
• Linter is clean
• No banned language patterns — this PR removes the last Python file (RSR-H4)
• No unsafe blocks without // SAFETY: — n/a
• No banned functions
• SPDX license header present on abi-ffi-gate.jl (MPL-2.0)
• No secrets, credentials, or .env files

As Applicable

• ABI/FFI changes validated — the conformance gate's behaviour is preserved (verified below)
• State files / CHANGELOG — no released-version change

Testing

Verified locally with julia 1.11.5 against this tree:

# OK path is byte-identical to the Python it replaces:
$ diff <(python3 abi-ffi-gate.py) <(julia abi-ffi-gate.jl)   → identical
  ABI-FFI GATE: OK (verisimiser) — 24 ABI functions exported, 8 result codes match   (exit 0)

Adversarial (the gate must fail on drift) — each returns exit 1 with the right diagnosis:

Injected drift	Result
null_pointer = 4 → 9 in the Zig enum	❌ "Result-code map differs (name or value)"
remove an export fn	❌ "1 ABI function(s) not exported by the Zig FFI"
add a {{PROJECT_NAME}} token to the Zig	❌ "Zig FFI has unrendered template tokens"

So the port is behaviour-equivalent and non-vacuous.

Screenshots

n/a (script + workflow)

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🤖 Generated with Claude Code

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Generated by Claude Code