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/0790-modules-same-name-const-cross-cycle-guard/a.sx

@@ -0,0 +1,4 @@
+// Module A authors `M :: 1` and `K :: M + 1` (= 2). A's `K` folds its leaf `M`
+// against A's own `M`.
+M :: 1;
+K :: M + 1;

examples/modules/0790-modules-same-name-const-cross-cycle-guard/b.sx

@@ -0,0 +1,6 @@
+// Module B flat-imports A and authors a DIFFERENT same-name `M :: K + 1` (= 3),
+// reading A's `K`. Folding B's `M` walks B's `M` → A's `K` → A's `M` — the name
+// `M` recurs across two modules. The cycle guard must NOT confuse B's `M` with
+// A's `M`: keyed on (name, source) the chain folds to 3.
+#import "a.sx";
+M :: K + 1;