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/toml_datetime-17254934f34d7094/lib-toml_datetime.json

@@ -0,0 +1 @@
+{"rustc":11835527281324007204,"features":"[\"alloc\", \"serde\", \"std\"]","declared_features":"[\"alloc\", \"default\", \"serde\", \"std\"]","target":6829622772598562593,"profile":15030774072793220737,"path":17055720938019569681,"deps":[[11029742160753049355,"serde_core",false,7622725113838073075]],"local":[{"CheckDepInfo":{"dep_info":"debug/.fingerprint/toml_datetime-17254934f34d7094/dep-lib-toml_datetime","checksum":false}}],"rustflags":[],"config":9396254390672932401,"compile_kind":0}