Gate r1 (2c + quality, Low): with no stored row, TUI/Desktop /save json
wrote the legacy {model, session_id, session_start, system_prompt,
messages} shape. It has no `id`, so import_sessions rejected it
("session id is required") while every other /save json file imports.
Use the CLI fallback's canonical keys (id = the live row key,
started_at as an epoch or None); keep system_prompt as an extra key.
No reader of the old keys exists in apps/, ui-tui/ or web/.
399eac705f