Retain source nodes for unchanged scalar values and string keys when
replacing a Hermes registration. Discarding quoted YAML 1.2 keys could
make Hermes' C reader reject duplicate boolean keys and switch to the
pure reader, changing the interpretation of unrelated settings.
Use linear mapping lookup, quote newly created YAML 1.2 strings for
YAML 1.1 compatibility, and preserve direct numeric edit formatting.
Extend actual CLI coverage for both existing reader-selection directions;
verify strings, exact unrelated numeric/timestamp values, backups and
idempotence with the actual Hermes Python loader.
Follow-up to #3102 and main's independent Hermes scalar fix.
Co-authored-by: Kaoru0822 <208281322+kaoru0822-kitauji@users.noreply.github.com>
Co-authored-by: gensokyo-dev <342580529+gensokyo-dev@users.noreply.github.com>
