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/0709-modules-issue-0056/common.sx

@@ -0,0 +1,12 @@
+// A parameterised-protocol (`Into`) impl living in a module reachable through
+// more than one import path. Each path must NOT re-register the impl.
+// Impl blocks are anonymous (`declName() == null`), so the diamond-import
+// dedup in imports.zig (`mergeFlat`) skips them and appends the node once per
+// path — `registerParamImpl` then trips its same-file duplicate check.
+Wrapped :: struct { v: s64; }
+
+impl Into(Wrapped) for s64 {
+    convert :: (self: s64) -> Wrapped {
+        return .{ v = self };
+    }
+}

examples/0709-modules-issue-0056/mid_a.sx

@@ -0,0 +1,3 @@
+#import "common.sx";
+
+mid_a_marker :: () -> s64 { 1; }

examples/0709-modules-issue-0056/mid_b.sx

@@ -0,0 +1,3 @@
+#import "common.sx";
+
+mid_b_marker :: () -> s64 { 2; }