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/0603-comptime-interp-variadic-any.sx

@@ -0,0 +1,29 @@
+// IR interpreter — variadic `..Any` indexing inside post-link callback.
+//
+// `format(fmt, ..args: []Any)` lowers to `any_to_string(args[i])` calls.
+// The interpreter must be able to read every element of the packed
+// `[N x Any]` slice from within a `#run`/post-link callback, not just
+// the first two — and not just via JIT.
+
+#import "modules/std.sx";
+#import "modules/compiler.sx";
+
+puts :: (s: [:0]u8) -> s32 #foreign libc;
+
+cb :: () -> bool {
+    a := format("{}", "x");
+    puts("1-arg ok");
+    b := format("{} {}", "x", "y");
+    puts("2-arg ok");
+    c := format("{} {} {}", "x", "y", "z");
+    puts("3-arg ok");
+    true;
+}
+
+configure :: () {
+    opts := build_options();
+    opts.set_post_link_callback(cb);
+}
+#run configure();
+
+main :: () { print("rt\n"); }