fix(ml-mcp): add HuggingFaceResource enum to Zig FFI (standards#152) (#122)

Class C ABI gap. `HuggingFaceResource` (4 variants, `hfResourceToInt`
1–4) was Idris2-only.

`iseriser abi-verify` → exit 0 (3 enums, 6 transitions); `zig build
test` → 24/24 green.

Closes hyperpolymath/standards#152
Refs hyperpolymath/standards#92, #89

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

cartridges/ml-mcp/ffi/ml_ffi.zig

@@ -25,6 +25,16 @@ pub const MlProvider = enum(c_int) {
     custom = 99,
 };
 
+/// Hugging Face resource types — mirrors `MlMcp.SafeMl.HuggingFaceResource`
+/// + `hfResourceToInt` encoding. Declared here so `iseriser abi-verify`
+/// can structurally check the encoding against the Idris2 source.
+pub const HuggingFaceResource = enum(c_int) {
+    hf_model = 1,
+    hf_space = 2,
+    hf_dataset = 3,
+    hf_inference = 4,
+};
+
 // ═══════════════════════════════════════════════════════════════════════
 // Session State Machine
 // ═══════════════════════════════════════════════════════════════════════