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/0414-protocols-generic-struct-protocol-erase.sx

@@ -0,0 +1,33 @@
+// Phase 6 / issue 0054 — generic-struct → parameterized-protocol erasure.
+//   - A generic-struct impl method `self: *Box` now resolves `self.field` to the
+//     concrete INSTANCE (the template name binds to the instance type), so
+//     `self.x` works (was "field not found on type 'Box'").
+//   - `xx c` erases a generic-struct instance (`Combined__s64_s64`) to a
+//     parameterized protocol (`VL(s64)`) via the generic
+//     `impl VL($R) for Combined($R, ..$Ts)`: the thunk monomorphizes the
+//     template method for the instance and dispatch works (was a trap).
+
+#import "modules/std.sx";
+
+VL :: protocol(T: Type) { get :: () -> T; }
+IntCell :: struct { v: s64; }
+impl VL(s64) for IntCell { get :: (self: *IntCell) -> s64 => self.v; }
+
+Combined :: struct($R: Type, ..$Ts: []Type) {
+    sources: (..VL(Ts));
+    value:   $R;
+}
+impl VL($R) for Combined($R, ..$Ts) { get :: (self: *Combined) -> $R => self.value; }
+
+make :: (..sources: VL) -> VL(s64) {
+    c : Combined(s64, ..sources.T) = ---;
+    c.value = 99;
+    c.sources = (..sources);
+    return xx c;                 // Combined__s64_s64 -> VL(s64)
+}
+
+main :: () -> s32 {
+    r := make(IntCell.{ v = 1 });
+    print("{}\n", r.get());      // 99 (dispatch through the erased Combined)
+    0;
+}