When tablet_session_mode='session_swap', the server attributes every
write via request.env.user — there's no need to pass tablet_tech_id
in the RPC params. Caches the mode lookup at module level so we don't
round-trip on every RPC.
Legacy mode unchanged — fpRpc still injects tablet_tech_id from
techStore.currentTechId.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
6d4b6284ad
