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/errors/1034-errors-interp-frames.sx

@@ -0,0 +1,23 @@
+// `trace.print_interpreter_frames()` (ERR step E4.1). At comptime (`#run`) it
+// dumps the interpreter's active sx call-frame chain (most recent call last) to
+// the build output; in compiled code it folds to nothing (no interpreter stack
+// — the only real caller is `process.exit`'s dead `is_comptime()` branch). The
+// dump frame itself is omitted; frame source locations await IR-offset
+// resolution, so only names print today. Expected exit: 0.
+
+#import "modules/std.sx";
+trace :: #import "modules/std/trace.sx";
+
+probe :: () {
+    trace.print_interpreter_frames();    // dumps the chain: __run_0 → inner → probe
+}
+
+inner :: () {
+    probe();
+}
+
+#run inner();                             // top-level #run drives the chain
+
+main :: () -> i32 {
+    return 0;
+}