- Register endpoint: replace 'nick is claimed and can be reclaimed
later' with accurate description that login adds clients while
session remains active
- Wrap line 205 (120 chars) after 'all-client removal.'
- Wrap line 2592 (115 chars) after 'never required.'
The README incorrectly claimed that registered sessions persist across
logouts. The actual code (handleQuit and cleanupUser in api.go) deletes
ALL sessions unconditionally when the last client disconnects — no check
for password_hash.
Updated Data Lifecycle, Registered Accounts, Identity & Sessions rationale,
flow diagram, and Design Principles to accurately state that both anonymous
and registered sessions are deleted on QUIT or last-client-logout.
Registration enables multi-client access (login from another device while
session is active), not session persistence across all-client removal.