feat: add stdlib module support with auto-import resolution

- Parse module paths in stdlib (module Std::Array { ... })
- Collect stdlib declarations and inject into user modules before sema
- Add dkExternFunc support throughout pipeline (parser, sema, hir, c backend)
- Auto-dereference pointer types for field access (arr->field)
- Add hArrowField HIR node for cleaner C emission
- Fix resolveTypeExpr for pointer and cast types
- Fix struct field lowering to use resolveTypeExpr
- Allow int <-> uint implicit conversion for bootstrap convenience
- Add stdlib/Std/Array.bux with dynamic array primitives
- Add stdlib_test demonstrating Array usage via import Std::Array::{Array};

stdlib/Std/Array.bux

@@ -0,0 +1,44 @@
+module Std::Array {
+
+extern func bux_alloc(size: uint) -> *void;
+extern func bux_realloc(ptr: *void, size: uint) -> *void;
+extern func bux_free(ptr: *void);
+extern func bux_bounds_check(index: uint, len: uint);
+
+struct Array {
+    data: *int,
+    len: uint,
+    cap: uint,
+}
+
+func Array_New(cap: uint) -> Array {
+    let data = bux_alloc(cap * 8) as *int;
+    return Array { data: data, len: 0, cap: cap };
+}
+
+func Array_Push(arr: *Array, value: int) {
+    if arr.len >= arr.cap {
+        arr.cap = arr.cap * 2;
+        arr.data = bux_realloc(arr.data as *void, arr.cap * 8) as *int;
+    }
+    arr.data[arr.len] = value;
+    arr.len = arr.len + 1;
+}
+
+func Array_Get(arr: *Array, index: uint) -> int {
+    bux_bounds_check(index, arr.len);
+    return arr.data[index];
+}
+
+func Array_Len(arr: *Array) -> uint {
+    return arr.len;
+}
+
+func Array_Free(arr: *Array) {
+    bux_free(arr.data as *void);
+    arr.data = null as *int;
+    arr.len = 0;
+    arr.cap = 0;
+}
+
+}