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/platform/1646-platform-asm-value-binding.sx

@@ -0,0 +1,9 @@
+// ASM stream Phase D — a bare `x := asm { … -> T }` binding (not a direct
+// `return asm`) types correctly: the value output flows through the local and
+// out as the exit code. Regression for the `inferType` `.asm_expr` arm (without
+// it the binding inferred `.unresolved` and silently produced 0). aarch64-pinned
+// via `.build` → runs on a matching host, ir-only elsewhere.
+main :: () -> i64 {
+    x := asm { "mov %[out], #99", [out] "=r" -> i64 };
+    return x;
+}