Two log-spam bugs found in live gateway logs:
1. gateway_routing UNIQUE-constraint spam (261 warnings in one errors.log):
early builds of the #59203 routing-index migration created
gateway_routing with 'session_key TEXT PRIMARY KEY' and no scope
column. _reconcile_columns() ADDs the missing scope column but SQLite
cannot ALTER a primary key, so the shipped composite
PRIMARY KEY (scope, session_key) never lands on those databases. Both
write paths then fail on every save:
- save_gateway_routing_entry: 'ON CONFLICT clause does not match any
PRIMARY KEY or UNIQUE constraint'
- replace_gateway_routing_entries: 'UNIQUE constraint failed:
gateway_routing.session_key' whenever the same session_key exists
under another scope (e.g. test-suite scopes leaked into a live DB).
New _heal_gateway_routing_pk() rebuilds the table once with the
composite key, preserving rows (newest wins on collisions, NULL scope
coalesced to ''). Same one-time-heal pattern as the #51646 active-
column repair. Verified E2E against a copy of a real affected state.db.
2. pre_gateway_dispatch warned ''GatewayRunner' object has no attribute
'session_store'' and silently dropped the hook for every message on
partially-initialized runners (bare object.__new__ runners in tests,
and any future init-order change). Pass
getattr(self, 'session_store', None) so the hook always fires
(pitfall #17 pattern).
Both regression tests fail without their fixes (sabotage-verified).