feat(checker): examples() and spec_files() carry the specification's files

A consumer of the checker crate needs no path into this repository.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HS8WZziDnyxunC23MUxrLp

target/debug/.fingerprint/include_dir_macros-47a75299d5c0751b/lib-include_dir_macros.json

@@ -0,0 +1 @@
+{"rustc":11835527281324007204,"features":"[]","declared_features":"[\"metadata\", \"nightly\"]","target":2599096113492287683,"profile":11528375766455597691,"path":12052302112748780107,"deps":[[8949245912927223590,"quote",false,6148210718780026669],[16346726298725429545,"proc_macro2",false,12044787672170069212]],"local":[{"CheckDepInfo":{"dep_info":"debug/.fingerprint/include_dir_macros-47a75299d5c0751b/dep-lib-include_dir_macros","checksum":false}}],"rustflags":[],"config":9396254390672932401,"compile_kind":0}