The base settings.toml is tracked; the new sibling settings.local.toml
is gitignored (entry already at .gitignore:32 — it was aspirational
until now, since the loader only read one file).
`load_config()` now overlays the local file on top of the base via a
new `_overlay_sections` helper that merges one level deep: for each
section in the local file, its keys are merged onto the base section's
keys, so a local `[database] url = "..."` no longer wipes other
`[database]` keys in the base. Sections present in only one file pass
through untouched.
Overlay is resolved as a sibling of whichever base file was chosen, so
SECOND_BRAIN_CONFIG=/etc/sb/settings.toml also picks up the matching
/etc/sb/settings.local.toml.
This is the dev-side ergonomic fix: Travis's interactive shell can keep
the lovebug password in a gitignored, 0600 settings.local.toml instead
of needing SECOND_BRAIN_DATABASE_URL exported on every manual `process`
run. Existing _merge is untouched (shallow), so the per-section
property merges in Config keep current semantics.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
