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/0410-protocols-impl-visibility-impl.sx

@@ -1,7 +1,7 @@
 // Helper that defines the impl. 179-impl-visibility's user file does NOT
 // directly import this — that's the whole point of the test.
 #import "modules/std.sx";
-#import "./179-impl-visibility-types.sx";
+#import "./0410-protocols-impl-visibility-types.sx";
 
 impl Into(Wrap) for s64 {
   convert :: (self: s64) -> Wrap {

examples/0410-protocols-impl-visibility-user.sx

@@ -1,7 +1,7 @@
 // User file uses xx but only imports the shared types — NOT the impl.
 // The Phase 4 visibility filter should reject the impl from 179-impl-visibility-impl.sx.
 #import "modules/std.sx";
-#import "./179-impl-visibility-types.sx";
+#import "./0410-protocols-impl-visibility-types.sx";
 
 run_user :: () -> s32 {
   w : Wrap = xx 7;

examples/0410-protocols-impl-visibility.sx

@@ -15,7 +15,7 @@
 // expected output. Tests/expected/.txt captures it; .exit is 1.
 
 #import "modules/std.sx";
-#import "./179-impl-visibility-impl.sx";
-#import "./179-impl-visibility-user.sx";
+#import "./0410-protocols-impl-visibility-impl.sx";
+#import "./0410-protocols-impl-visibility-user.sx";
 
 main :: () -> s32 { run_user(); }

examples/0411-protocols-impl-duplicate-impl-a.sx

@@ -1,6 +1,6 @@
 // Helper A — one of two conflicting impls for the same (s64, Wrap) pair.
 #import "modules/std.sx";
-#import "./180-impl-duplicate-types.sx";
+#import "./0411-protocols-impl-duplicate-types.sx";
 
 impl Into(Wrap) for s64 {
   convert :: (self: s64) -> Wrap {

examples/0411-protocols-impl-duplicate-impl-b.sx

@@ -1,6 +1,6 @@
 // Helper B — second conflicting impl for the same (s64, Wrap) pair.
 #import "modules/std.sx";
-#import "./180-impl-duplicate-types.sx";
+#import "./0411-protocols-impl-duplicate-types.sx";
 
 impl Into(Wrap) for s64 {
   convert :: (self: s64) -> Wrap {

examples/0411-protocols-impl-duplicate.sx

@@ -13,8 +13,8 @@
 // both impl modules.
 
 #import "modules/std.sx";
-#import "./180-impl-duplicate-impl-a.sx";
-#import "./180-impl-duplicate-impl-b.sx";
+#import "./0411-protocols-impl-duplicate-impl-a.sx";
+#import "./0411-protocols-impl-duplicate-impl-b.sx";
 
 main :: () -> s32 {
   w : Wrap = xx 7;