fix(0127): namespaced generic calls type their result from the call's bindings

The plan producer's namespace-fn arms returned the declared return type
without checking type_params, so a qualified generic call's result
carried the unbound T stub: print boxed it as 'T{}', and a non-s64
binding failed LLVM verification (pack monomorphized for the stub,
call returning double). Both fn_ast_map-backed arms now classify
generic callees as generic_fn and infer the return through
inferGenericReturnType, mirroring the bare-identifier path.

examples/0213-generics-namespaced-call-result.sx

@@ -0,0 +1,13 @@
+// A NAMESPACED call to a generic free function types its result from the
+// call's inferred bindings — not the unbound `T` stub (issue 0127:
+// `m.pick(3, 9)` boxed as `T{}` while the flat spelling printed `9`).
+#import "modules/std.sx";
+m :: #import "0213-generics-namespaced-call-result/m.sx";
+
+main :: () {
+    print("{}\n", m.pick(3, 9));        // s64 binding
+    print("{}\n", m.pick(1.5, 0.25));   // f64 binding
+    v := m.double(21);
+    w : s64 = v + 0;                    // the concrete type flows onward
+    print("{}\n", w);
+}

examples/0213-generics-namespaced-call-result/m.sx

@@ -0,0 +1,9 @@
+#import "modules/std.sx";
+
+pick :: (a: $T, b: T) -> T {
+    if a > b then a else b
+}
+
+double :: (x: $T) -> T {
+    x + x
+}

examples/expected/0213-generics-namespaced-call-result.exit

@@ -0,0 +1 @@
+0

examples/expected/0213-generics-namespaced-call-result.stderr

@@ -0,0 +1 @@
+

examples/expected/0213-generics-namespaced-call-result.stdout

@@ -0,0 +1,3 @@
+9
+1.500000
+42