feat(resolver): source-aware nominal leaf (Lowering-side) + ns-const tightening [stdlib E1]

Route the Lowering-side bare type leaf through the source-keyed caches (E0):
nominal author via collectVisibleAuthors(.user_bare_flat) + alias via
type_aliases_by_source, instead of the global findByName first-match. The
binding-free resolveAstType path + registration sites stay on the global
compat readers (move later). Single-author resolution byte-identical (no
shadows yet). Folded req #1: a namespaced-only import's const is no longer
bare-visible in array-dim/comptime-scalar position. Adds regression 0742
(ns-only bare const) and 0210 (generics/Vector/type-fn stay legacy).

Salvaged from a worker killed at the wall before commit; manager verified
the gate at ground truth (zig build test exit 0; run_examples 479/0 with
0210+0742 ok, prior 477 byte-identical; m3te ios-sim exit 0; folded fix
confirmed fail-before on master 7ffc0c1 exit 0 / pass-after exit 1).

examples/expected/0210-generics-resolver-legacy-paths.exit

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

examples/expected/0210-generics-resolver-legacy-paths.stderr

@@ -0,0 +1 @@
+

examples/expected/0210-generics-resolver-legacy-paths.stdout

@@ -0,0 +1,3 @@
+box: 42
+vec: 1.000000 4.000000
+typefn: len=3 a0=10 a2=30

examples/expected/0742-modules-namespaced-only-bare-const-not-visible.exit

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

examples/expected/0742-modules-namespaced-only-bare-const-not-visible.stderr

@@ -0,0 +1,5 @@
+error: array dimension must be a compile-time integer constant
+  --> examples/0742-modules-namespaced-only-bare-const-not-visible.sx:13:12
+   |
+13 |     arr : [DEP_LEN]s32 = ---;
+   |            ^^^^^^^

examples/expected/0742-modules-namespaced-only-bare-const-not-visible.stdout

@@ -0,0 +1 @@
+