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/proc-macro2-ab005e1b49b4395b/build-script-build-script-build.json

@@ -0,0 +1 @@
+{"rustc":11835527281324007204,"features":"[\"default\", \"proc-macro\"]","declared_features":"[\"default\", \"nightly\", \"proc-macro\", \"span-locations\"]","target":5408242616063297496,"profile":11528375766455597691,"path":77739810642161920,"deps":[],"local":[{"CheckDepInfo":{"dep_info":"debug/.fingerprint/proc-macro2-ab005e1b49b4395b/dep-build-script-build-script-build","checksum":false}}],"rustflags":[],"config":9396254390672932401,"compile_kind":0}