Port from qwibitai/nanoclaw#3260: adds a third unauthorized_dm_behavior
option, 'decline'. Instead of replying with a pairing code (pair) or
staying silent (ignore), the gateway sends one short, polite decline to
the unknown sender, then stays silent toward that sender for 24 hours.
- gateway/config.py: accept 'decline' in the normalizer; new
unauthorized_dm_decline_message for custom decline text (round-trips
through to_dict/from_dict).
- gateway/pairing.py: persisted decline stamps (_declined.json) on
PairingStore with has_recent_decline/record_decline; stamps are
pruned on write and recorded BEFORE delivery so a send failure can't
become a decline storm (nanoclaw's stamp-first pattern).
- gateway/run.py: decline branch in the unauthorized-sender path;
groups still always silently ignore.
- docs: security.md + configuration.md updated.
Adapted from TypeScript (NanoClaw's pending_sender_approvals 'decline:'
stamp rows) to Hermes' existing PairingStore JSON persistence; the
owner-FYI half of nanoclaw's flow is intentionally not ported — Hermes
logs the unauthorized attempt, and pairing remains the owner-visible
grant path.
Rebase onto the decomposed gateway (salvage, #88028):
- The unauthorized-sender path moved from gateway/run.py to
gateway/run_inbound.py::_hm_admit_event; the decline branch is a sibling
helper _hm_send_unauthorized_decline next to _hm_offer_pairing_code.
- gateway/config.py now validates the enum via _normalize_choice; the
accepted set is the module constant UNAUTHORIZED_DM_BEHAVIORS (used by
both from_dict and get_unauthorized_dm_behavior so a per-platform
`extra.unauthorized_dm_behavior: decline` is honoured too). The default
decline text lives in config as DEFAULT_UNAUTHORIZED_DM_DECLINE_MESSAGE.
- Tests trimmed from 5 to 2 invariant tests (send-once-then-silent through
the real inbound path; config round-trip + real PairingStore stamp
lifecycle with a patched clock instead of rewriting the JSON file).
a6e934e0fd