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/1052-errors-cleanup-transitive-reject.sx

@@ -0,0 +1,36 @@
+// The cleanup-absorption check (ERR step E1.7) is TRANSITIVE: a bare,
+// un-absorbed failable call is rejected no matter how deeply it is nested
+// inside a `defer` / `onfail` body's control flow — through `if` (both
+// branches), nested blocks, and loops. 1049 covers the direct-body case; this
+// pins the recursive arms of `checkCleanupNode` (`.if_expr`, `.block`,
+// `.while_expr`) before A5.2 extracts the pass into its own module.
+//
+// Three bare failables, three rejections; the program never runs (exit 1).
+
+#import "modules/std.sx";
+
+E :: error { Bad }
+
+failing :: () -> !E { raise error.Bad; }
+
+work :: (n: i32) -> !E {
+    defer {
+        if n > 0 {
+            failing();              // REJECTED: nested in the `if` then-branch
+        } else {
+            { failing(); }          // REJECTED: nested block in the else-branch
+        }
+    }
+    onfail {
+        while n > 0 {
+            failing();              // REJECTED: nested in the `while` body
+        }
+    }
+    if n < 0 { raise error.Bad; }
+    return;
+}
+
+main :: () -> i32 {
+    a := work(-1);
+    return 0;
+}