test: group examples into per-category folders

Move examples/*.sx and their expected/ snapshots into per-category
subfolders (examples/<category>/...). Folder = leading filename token,
with ffi-objc/ffi-jni kept whole; filenames are unchanged. The corpus
runner and LSP sweep now discover each category's expected/ dir, while
issues/ stays flat. Example 1058's repo-root-relative companion import
is made file-relative. Path strings embedded in 164 snapshots were
regenerated (path-only changes). Test-layout docs in CLAUDE.md updated.

examples/modules/0758-modules-same-name-struct-mutual-ref/a.sx

@@ -0,0 +1,3 @@
+// Module A authors its OWN `Box` and `Node` (the FIRST same-name authors).
+Box  :: struct { x: i64; }
+Node :: struct { n: i64; }

examples/modules/0758-modules-same-name-struct-mutual-ref/b.sx

@@ -0,0 +1,13 @@
+// Module B authors same-name `Box` and `Node` shadows that reference EACH OTHER.
+// B's `Box` has a FORWARD ref to B's `Node` (declared after it), and B's `Node`
+// back-refs B's `Box`. Both forward and mutual refs must resolve to B's OWN
+// nominal TypeIds, not the first same-name authors in A.
+Box  :: struct { y: i64; peer: *Node; }
+Node :: struct { m: i64; owner: *Box; }
+b_test :: () -> i64 {
+    nd := Node.{ m = 99, owner = null };
+    bx := Box.{ y = 7, peer = @nd };
+    // Reads B's Node.m (99); pre-fix the forward ref bound to A's Node (which has
+    // field `n`, not `m`) → "field 'm' not found on type 'Node'".
+    return bx.peer.*.m;
+}