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/1013-errors-value-failable-reject.sx

@@ -0,0 +1,19 @@
+// Value-carrying `catch` rejection (ERR step E2.1b): when the failable LHS
+// carries a value, a non-diverging catch handler must produce a value of the
+// success type — a value-less (void) body is a type error (otherwise the
+// success and error paths couldn't merge to one value). Diverge instead
+// (`return` / `raise`) or yield a value. Positives: `examples/229-value-failable-consume.sx`.
+
+#import "modules/std.sx";
+
+E :: error { Bad }
+
+parse :: (n: s32) -> (s32, !E) {
+    if n < 0 { raise error.Bad; }
+    return n;
+}
+
+main :: () -> s32 {
+    x := parse(-1) catch e { print("oops\n"); };   // error: body yields no value
+    return x;
+}