A possibly-dotted key, e.g. physical.shape or "a"."b".c.
Stored as the ordered list of its parts plus the verbatim raw
source text (including any whitespace around the dots), so the
serializer can re-emit the key byte-for-byte.
Instance methods
path
The logical path of this key as an Array(String) (decoded).
Convenience: shorthand for path.join('.'). Useful for error
messages but not for storage — TOML keys with dots in them are
legal and would round-trip incorrectly through this method.