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/1038-errors-comptime-run-handled.sx

@@ -0,0 +1,31 @@
+// Comptime `#run` of a failable composes with the handlers exactly as at
+// runtime: `catch` absorbs, `or` terminates, a successful bare `#run` yields the
+// value (error channel stripped), and an `onfail` in the evaluated body still
+// runs during comptime unwinding (E5.2).
+
+#import "modules/std.sx";
+
+E :: error { Bad, Empty }
+
+parse :: (n: i32) -> (i32, !E) {
+    if n < 0  { raise error.Bad; }
+    if n == 0 { raise error.Empty; }
+    return n * 2;
+}
+
+guard :: (ok: bool) -> !E {
+    onfail print("comptime cleanup\n");
+    if !ok { raise error.Bad; }
+    return;
+}
+
+ok_v   :: #run parse(5);            // success → 10 (value, error stripped)
+caught :: #run parse(-1) catch (e) 99; // Bad   → 99
+ored   :: #run parse(0) or 55;       // Empty → 55
+
+#run guard(false) catch (e) { };       // onfail fires during the comptime unwind
+
+main :: () -> i32 {
+    print("ok={} caught={} ored={}\n", ok_v, caught, ored);
+    return ok_v + caught + ored;     // 10 + 99 + 55 = 164
+}