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/1032-errors-assert.sx

@@ -0,0 +1,15 @@
+// `assert` (ERR steps E4.1 / E4.1b): a false condition prints `ASSERTION
+// FAILED at <file>:<line>: <msg>` (the caller's location, via the
+// `#caller_location` default param) and exits 1; a true condition is a no-op.
+// Built on `process.exit`. Expected exit code: 1.
+
+#import "modules/std.sx";
+proc :: #import "modules/process.sx";
+
+main :: () -> s32 {
+    proc.assert(2 + 2 == 4, "arithmetic");                 // passes → no-op
+    print("first assert passed\n");
+    proc.assert(2 + 2 == 5, "two plus two is not five");   // fails → abort
+    print("unreachable\n");
+    return 0;
+}