feat(zig): native Arboricx bundle parser and C ABI

ext/zig/src/kernel.zig

@@ -0,0 +1,22 @@
+const std = @import("std");
+const tree = @import("tree.zig");
+const Arena = @import("arena.zig").Arena;
+const embed = @import("kernel_embed");
+
+/// Copy the embedded kernel into an arena, returning the new root index.
+/// This allows the kernel to be used in App nodes alongside application terms.
+pub fn loadKernel(arena: *Arena) !u32 {
+    var mapping = try arena.allocator.alloc(u32, embed.kernel_nodes.len);
+    defer arena.allocator.free(mapping);
+
+    for (embed.kernel_nodes, 0..) |node, i| {
+        const idx: u32 = @intCast(i);
+        mapping[idx] = switch (node) {
+            .leaf => try arena.alloc(.leaf),
+            .stem => |s| try arena.alloc(.{ .stem = .{ .child = mapping[s.child] } }),
+            .fork => |f| try arena.alloc(.{ .fork = .{ .left = mapping[f.left], .right = mapping[f.right] } }),
+        };
+    }
+
+    return mapping[embed.kernel_root];
+}