test: migrate examples to XXXX-category-name layout + split expected streams

Rename all example tests/companions to the XXXX-category-test-name scheme
(per-category 100-blocks: basic 0010, types 0100, ... errors 1000,
diagnostics 1100, ffi 1200, ffi-objc 1300, ffi-jni 1400, vectors 1500,
platform 1600). Companions and dir/C fixtures move in lockstep with their
parent test; #import/#source/#include paths rewritten to match.

Expected output now lives in examples/expected/ (a sibling dir of the
tests) split into three streams per the new convention:
  <name>.exit / <name>.stdout / <name>.stderr  (+ optional <name>.ir)

run_examples.sh rewritten: scans examples/ and issues/ for an
expected/<name>.exit marker, captures stdout and stderr separately (no
more 2>&1), compares each stream + exit + optional IR snapshot.

Behavior validated unchanged: every renamed test reproduces its prior
merged output + exit (diffs limited to file paths/basenames embedded in
diagnostics + traces, which correctly reflect the new names). Suite:
292 passed, 0 failed. 50-smoke.sx split + issue relocation + docs follow
in subsequent commits.

examples/0707-modules-import-dir-scan-order.sx

@@ -0,0 +1,29 @@
+// Regression test for issue-0039 — directory-import scan order.
+//
+// When a directory is imported, the resolver iterates files
+// alphabetically. Inside the directory, `aaa_uses.sx` comes BEFORE
+// `types.sx` but its `make_my` returns `MyEnum` (defined in
+// `types.sx`). The combined directory module must put `aaa_uses.sx`'s
+// transitive imports (which include `MyEnum`) into the global scan
+// stream BEFORE `aaa_uses.sx`'s own decls so the tagged_union for
+// MyEnum is registered before `make_my`'s return type is resolved.
+//
+// Pre-fix, the dir-import implementation appended each file's
+// `own_decls` before its `decls`, which inverted that order and
+// caused `MyEnum` to be registered as a placeholder struct via the
+// `resolveTypeName` fallback. The later `enum_decl` scan then
+// short-circuited via `findByName` and never upgraded the placeholder
+// to the real tagged_union, surfacing as "cannot infer enum type
+// for '.b'" at the `return .b(42)` site.
+
+#import "modules/std.sx";
+#import "0707-modules-import-dir-scan-order";
+
+main :: () -> s32 {
+    e := make_my();
+    if e == {
+        case .a: { print("a\n"); }
+        case .b: (v) { print("b={}\n", v); }
+    }
+    0;
+}