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/ffi-objc/1309-ffi-objc-class-method-lowering.sx

@@ -0,0 +1,42 @@
+// M1.2 A.2c / A.3 — instance-method body lowering on sx-defined
+// `#objc_class`.
+//
+// The Obj-C runtime invokes class methods via the IMP pointers
+// wired up in M1.2 A.4. No sx-side call path drives lazy lowering,
+// so the eager pass `lowerObjcDefinedClassMethods` walks the
+// `objc_defined_class_cache` and force-lowers every bodied method
+// after Pass 1 finishes.
+//
+// `*Self` substitution (A.2b) routes the param's pointee type to
+// the hidden state-struct `__<ClassName>State`. `self.counter`
+// then resolves as a plain struct field access — A.3's "free if
+// types align". The IR snapshot pins the round-trip:
+//
+//   define internal void @SxFoo.bump(ptr __sx_ctx, ptr self) {
+//       %gep = getelementptr inbounds { i32 }, ptr %self, 0, 0
+//       %v = load i32, ptr %gep
+//       %inc = add i32 %v, 1
+//       store i32 %inc, ptr %gep
+//       ret void
+//   }
+//
+// IMP-trampoline emission (the C-ABI shim that the Obj-C runtime
+// calls and that reads the `__sx_state` ivar) lands separately
+// in M1.2 A.4 alongside class-pair init. Runtime dispatch
+// (M1.2 A.7) stays gated until then.
+
+#import "modules/std.sx";
+#import "modules/build.sx";
+
+SxFoo :: #objc_class("SxFoo") {
+    counter: i32;
+
+    bump :: (self: *Self) {
+        self.counter += 1;
+    }
+}
+
+main :: () -> i32 {
+    print("compiled\n");
+    0
+}