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/1609-platform-add-framework.sx

@@ -0,0 +1,20 @@
+// BuildOptions.add_framework registers an Apple framework at comptime,
+// equivalent to a top-level `#framework "Name"` directive. The advantage:
+// you can gate it with `inline if OS == .ios { ... }` or similar logic,
+// keeping the framework off non-Apple builds.
+
+#import "modules/std.sx";
+#import "modules/compiler.sx";
+
+configure_build :: () {
+    opts := build_options();
+    opts.add_framework("CoreFoundation");
+}
+#run configure_build();
+
+CFAbsoluteTimeGetCurrent :: () -> f64 #foreign;
+
+main :: () -> s32 {
+    t := CFAbsoluteTimeGetCurrent();
+    return if t > 0.0 then 0 else 1;
+}