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/0802-memory-pointers.sx

@@ -0,0 +1,28 @@
+#import "modules/std.sx";
+
+Vec2 :: struct { x, y: f32; }
+
+set_x :: (p: *Vec2, val: f32) {
+    p.x = val;
+}
+
+main :: () {
+    v := Vec2.{ 1.0, 2.0 };
+    print("before: {}\n", v);
+
+    set_x(@v, 99.0);
+    print("after: {}\n", v);
+
+    ptr := @v;
+    copy := ptr.*;
+    print("copy: {}\n", copy);
+    
+    // null pointer
+    np : *Vec2 = null;
+
+    // many-pointer indexing
+    arr : [5]s32 = .[10, 20, 30, 40, 50];
+    mp : [*]s32 = @arr[0];
+    print("mp[0] = {}\n", mp[0]);
+    print("mp[2] = {}\n", mp[2]);
+}