The pure, fully-tested half of the in-app sidecar editor. No new runtime
dependency: CI's test job installs only `pytest cryptography` (not
requirements.txt) and the catalog-signature job imports bcc_core with only
cryptography, and the workflow is off-limits — so a top-level TOML import is
impossible and any pip TOML dep would leave this code untested/red on CI.
- read_toml_section() — lenient, section-aware scalar reader (string/int/
float/bool); values it can't confidently decode are omitted (the writer
preserves them regardless).
- toml_sections() — ordered profile/section groups for the editor's picker.
- set_toml_value() / update_toml() — SURGICAL writer: rewrites only the one
key it's asked to, so comments, formatting, ordering and unknown keys/tables
round-trip untouched (strictly safer than parse->dict->reserialize, which
tomli-w wouldn't comment-preserve either). CRLF-preserving; correct scalar
quoting/escaping; creates a missing section; deletes on value=None.
- validate_sidecar_values() — enum/port validation against ServerSpec.schema
for the MANAGED fields only; unknown keys pass through (preserved, never a
save-blocker) — reconciles "reject out-of-enum" with "preserve unknown keys".
- write_sidecar() — atomic temp-write + os.replace + rotating backup (reuses
the extracted _atomic_write_text + _make_backup) then chmod 0600/0700 via
#93's fix_permissions. Never routes through apply_servers (cardinal rule).
- _make_backup() generalised to the file's own suffix (JSON naming unchanged),
so a .toml sidecar and a .json config keep separate backup pools.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
