`hermes_cli.config.atomic_config_write` is now THE config.yaml writer: it delegates to
`utils.atomic_roundtrip_yaml_save` (ruamel round-trip), which merges the new state onto the
on-disk document so user comments, key order, quoting and blank lines survive every write.
Why: config.yaml is hand-edited and commented, and every writer that re-serialised the parsed
dict through PyYAML (`save_config`, `config set/unset`, migrations, plugin bookkeeping, auth
provider reset, credential scrub, channel strip, backup restore, profile seed, telegram topic
persistence) destroyed those comments — and `save_config` re-appended the stock boilerplate on
top (#92554, #63039, #50698, #109611, #107511, #66752). The round-trip writer existed
(tui_gateway only) but nothing else used it, so each new writer regressed the class.
- save_config / _write_user_config / atomic_config_write -> round-trip merge; the commented
example blocks are appended only when the file is created.
- round-trip merge only reassigns nodes whose value changed (element-wise for lists), so an
untouched scalar/list keeps its inline comments; YAML 1.1-ambiguous strings (off/yes/no...)
are force-quoted at every depth; duplicate keys are tolerated like PyYAML.
- direct PyYAML writers in auth.py, credential_lifecycle.py, profile_channels.py, backup.py,
profiles.py, telegram adapter and tui_gateway/server.py now call atomic_config_write.
0706dffca1