test: group examples into per-category folders

Move examples/*.sx and their expected/ snapshots into per-category
subfolders (examples/<category>/...). Folder = leading filename token,
with ffi-objc/ffi-jni kept whole; filenames are unchanged. The corpus
runner and LSP sweep now discover each category's expected/ dir, while
issues/ stays flat. Example 1058's repo-root-relative companion import
is made file-relative. Path strings embedded in 164 snapshots were
regenerated (path-only changes). Test-layout docs in CLAUDE.md updated.

examples/memory/0808-memory-xx-value-routes-through-context-allocator.sx

@@ -0,0 +1,45 @@
+// Phase 1.1 — the compiler-internal heap-copy that backs `xx <rvalue>`
+// protocol erasure must dispatch through `context.allocator`, not call
+// libc malloc directly. So when a `push Context.{ allocator = tracer }`
+// block is active, a `xx StructLiteral.{}` inside it MUST be allocated
+// by the tracker.
+//
+// Note: `xx` only heap-copies for RVALUES (struct literals, call results).
+// `xx <lvalue>` (an identifier, field access, index, or deref) borrows
+// the operand's storage, so it never allocates and never reaches this
+// path. See specs.md §3 — Protocol value ownership and lifetime.
+#import "modules/std.sx";
+#import "modules/std/mem.sx"; // `Allocator` is non-transitive: name it, import it.
+
+Tracer :: struct {
+    count: i64;
+
+    init :: () -> *Tracer {
+        t : *Tracer = xx libc_malloc(size_of(Tracer));
+        t.count = 0;
+        t
+    }
+}
+
+impl Allocator for Tracer {
+    alloc_bytes :: (self: *Tracer, size: i64) -> *void {
+        self.count += 1;
+        return libc_malloc(size);
+    }
+    dealloc_bytes :: (self: *Tracer, ptr: *void) {
+        libc_free(ptr);
+    }
+}
+
+ByValue :: struct { x: i64; y: i64; }
+
+main :: () -> i32 {
+    tracer := Tracer.init();
+    push Context.{ allocator = xx tracer, data = null } {
+        // Struct-literal operand: rvalue → heap-copy through context.allocator.
+        ignore : Allocator = xx ByValue.{ x = 1, y = 2 };
+        _ = ignore;
+    }
+    print("Tracer.count = {}\n", tracer.count);
+    0
+}