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-121b4172b6fceaf7/lib-toml.json

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+{"rustc":11835527281324007204,"features":"[\"default\", \"display\", \"parse\", \"serde\", \"std\"]","declared_features":"[\"debug\", \"default\", \"display\", \"fast_hash\", \"parse\", \"preserve_order\", \"serde\", \"std\", \"unbounded\"]","target":5253204251445549666,"profile":10022867059850265794,"path":3214648938113924720,"deps":[[1697208404004473345,"toml_parser",false,10420484270566515435],[4298710645334413366,"toml_datetime",false,11327764612821415744],[4668767272702335084,"serde_spanned",false,9314642387481626447],[6338624599557368326,"winnow",false,8444054677671788009],[10434207171219547506,"toml_writer",false,13162133897511437189],[11029742160753049355,"serde_core",false,9186085954047428496]],"local":[{"CheckDepInfo":{"dep_info":"debug/.fingerprint/toml-121b4172b6fceaf7/dep-lib-toml","checksum":false}}],"rustflags":[],"config":9396254390672932401,"compile_kind":0}