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/0210-generics-resolver-legacy-paths.sx

@@ -0,0 +1,31 @@
+// Resolver E1 lock: the bare-type-leaf cutover to the source-aware
+// `selectNominalLeaf` must NOT touch the NON-leaf type heads. A generic-struct
+// instantiation (`Box(s32)`), a `Vector(N, T)` builtin, and a type-returning
+// function (`Make(3, s64)`) are all resolved by `resolveTypeWithBindings`
+// ABOVE the bare-name leaf switch (`resolveParameterizedWithBindings` /
+// `resolveTypeCallWithBindings` / the `Vector` builtin path), so they stay on
+// the legacy resolution and never reach `selectNominalLeaf`. Parameterized
+// protocols share the same `resolveParameterizedWithBindings` pre-leaf path
+// (covered by 0204/0206). This example pins that all three still resolve
+// identically after the cutover.
+#import "modules/std.sx";
+
+Box :: struct($T: Type) {
+    value: T;
+}
+
+Make :: ($K: u32, $T: Type) -> Type { return [K]T; }
+
+N :: 3;
+
+main :: () {
+    b : Box(s32) = .{ value = 42 };
+    print("box: {}\n", b.value);
+
+    v : Vector(4, f32) = .[1, 2, 3, 4];
+    print("vec: {} {}\n", v.x, v.w);
+
+    a : Make(N, s64) = ---;
+    a[0] = 10; a[2] = 30;
+    print("typefn: len={} a0={} a2={}\n", a.len, a[0], a[2]);
+}

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

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+// Bare module-const visibility under a NAMESPACED-only import — the const
+// sibling of 0736 (folded req #1 of the source-aware resolver, Phase E1).
+// `dep.sx` is imported only as `dep :: #import`, so its top-level `DEP_LEN`
+// is reachable ONLY as `dep.DEP_LEN`. A BARE `DEP_LEN` in a comptime
+// array-dimension position must NOT resolve: bare module-const visibility
+// joins over the FLAT import edges (`flat_import_graph`), and a namespaced
+// alias is not a flat edge. Before the fix the bare const leaked through the
+// global `module_const_map` first-match (and its float-fold fallback) straight
+// into the `[VAL]s32` dimension, so the array silently got length 3.
+dep :: #import "0742-modules-namespaced-only-bare-const-not-visible/dep.sx";
+
+main :: () -> s32 {
+    arr : [DEP_LEN]s32 = ---;
+    0
+}

examples/0742-modules-namespaced-only-bare-const-not-visible/dep.sx

@@ -0,0 +1 @@
+DEP_LEN :: 3;

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

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+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 @@
+