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/0413-protocols-parameterized-protocol-value.sx

@@ -0,0 +1,22 @@
+// Phase 4.2 — parameterized protocol as a runtime VALUE type. `VL(s64)` is a
+// 16-byte protocol value {ctx, vtable} (a plain protocol was already, but a
+// parameterized one used to resolve to a 0-field stub). A conforming struct
+// `xx`-erases into it, and method dispatch uses the bound type-arg
+// (`get -> T` becomes `get -> s64` for `VL(s64)`).
+
+#import "modules/std.sx";
+
+VL :: protocol(T: Type) { get :: () -> T; }
+IntCell :: struct { v: s64; }
+StrCell :: struct { s: string; }
+impl VL(s64) for IntCell { get :: (self: *IntCell) -> s64 => self.v; }
+impl VL(string) for StrCell { get :: (self: *StrCell) -> string => self.s; }
+
+main :: () -> s32 {
+    a : VL(s64) = xx IntCell.{ v = 42 };
+    print("a.get={}\n", a.get());          // 42 (T = s64)
+
+    b : VL(string) = xx StrCell.{ s = "hi" };
+    print("b.get={}\n", b.get());          // hi (T = string)
+    0;
+}