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.
example/1227 exposes the sx fn `sx_triple` to C under the symbol `triple_c`
via `export "triple_c"`; the companion C calls `triple_c` by that name.
RED: the define path emits the fn under its sx name (`sx_triple`) and
ignores the parsed `extern_name`, so the C reference to `triple_c` is
undefined at AOT link. The next commit consumes the rename on the define
path (gap iii) and greens it.
