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/0733-modules-flat-same-name-comptime-run/a.sx

@@ -0,0 +1,6 @@
+// a.sx authors `compute` returning 7 and evaluates it at comptime. Imported
+// first → first-wins winner; own == winner, but the #run must still lower in
+// a.sx's source context so the bare `compute` resolves at all (not ambiguous).
+compute :: () -> i64 { return 7; }
+A_VAL :: #run compute();
+get_a :: () -> i64 { return A_VAL; }

examples/modules/0733-modules-flat-same-name-comptime-run/b.sx

@@ -0,0 +1,6 @@
+// b.sx authors its OWN `compute` returning 70. Its `#run compute()` must bind
+// b.sx's author (70) — own-author wins in b.sx's source context — not the
+// first-wins winner from a.sx (7).
+compute :: () -> i64 { return 70; }
+B_VAL :: #run compute();
+get_b :: () -> i64 { return B_VAL; }