fix(lower): auto-ref compound lvalues passed to *T params

The implicit address-of that gives `*T` params reference semantics only
fired for plain identifiers (`mut(v)`). For a field-access / index /
deref lvalue (`make_move(self.board, m)`, `mut(w.s)`), the branch was
skipped: the arg was loaded into a temporary and the callee mutated a
throwaway copy — silent data loss, with the type check satisfied through
the temp so no diagnostic fired.

Now compound lvalues auto-ref too: take the real lvalue address via
`lowerExprAsPtr`, normalizing the "place" ref to `*T` exactly as
`@field_access` does. Mutations through the pointer are now visible to
the caller, matching the identifier case.

Regression: examples/255-autoref-compound-lvalue.sx.

examples/255-autoref-compound-lvalue.sx

@@ -0,0 +1,20 @@
+// Auto-ref of a COMPOUND lvalue (field access / index / deref) passed to a
+// `*T` parameter must reference the REAL lvalue, not a copy. Regression: a
+// field-access argument (e.g. `make_move(self.board, m)`) silently passed the
+// address of a temporary copy, so mutations through the pointer were lost with
+// no diagnostic. A plain local (`bump(x)`) already auto-ref'd; now compound
+// lvalues do too. Expected: w.s.v == 42 (the real field was mutated).
+
+#import "modules/std.sx";
+
+S :: struct { v: s32; }
+W :: struct { s: S; }
+
+bump :: (p: *S) { p.v = p.v + 41; }
+
+main :: () -> s32 {
+    w : W = .{ s = .{ v = 1 } };
+    bump(w.s);                       // field access, no `@` — auto-refs &w.s
+    print("w.s.v = {}\n", w.s.v);    // 42, not 1
+    return 0;
+}