fix(test): make property suite compile under pinned Zig 0.15.2

@typeinfo(...).@"enum".fields is comptime-only in 0.15.2; the three
runtime 'for' loops over enum fields (P7, P7b, P13) now use 'inline for'.
The suite had never compiled under the pinned toolchain (it is also not
run in CI), so the recorded test counts never included its 14 tests.
New verified baseline: 80 unit + 39 integration + 5 smoke + 14 property.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TaWWedv6VQqeZaPvc94keN

Author: claude

src/interface/ffi/test/property_test.zig

@@ -245,7 +245,7 @@ test "P7: ActionKind values are injective (no duplicates)" {
     // Collect all integer values into a fixed-size array and verify
     // no duplicates using a simple O(n^2) comparison (n=8, negligible cost).
     var seen: [fields.len]u8 = undefined;
-    for (fields, 0..) |f, i| {
+    inline for (fields, 0..) |f, i| {
         seen[i] = @intCast(f.value);
     }
 
@@ -268,7 +268,7 @@ test "P7b: ActionKind covers all 8 expected action types" {
 
     for (expected_names) |expected| {
         var found = false;
-        for (fields) |f| {
+        inline for (fields) |f| {
             if (std.mem.eql(u8, f.name, expected)) {
                 found = true;
                 break;
@@ -501,7 +501,7 @@ test "P13: ConfigFormat values are injective — no two variants share an intege
     const fields = @typeInfo(config_extract.ConfigFormat).@"enum".fields;
 
     var seen: [fields.len]u8 = undefined;
-    for (fields, 0..) |f, i| {
+    inline for (fields, 0..) |f, i| {
         seen[i] = @intCast(f.value);
     }