Get Perspective Sleep Report

TOS-2532 Phase 2: the smartwatch-style sleep report - one session's full stage timeline plus the trailing session series the report UI's trend strip plots. TOS-2265: same CHAT-ENTITLED access check as /sleep-status (check_chat_entitled_access) - the widening this docstring originally anticipated landing automatically via _check_perspective_access instead landed as its own dedicated check (see that function's docstring for why), so this call site was updated to match explicitly rather than silently staying owner-only.

TOS-2777: optional ?session_id= selects a PRIOR night's timeline so the report UI can page backward through history. Omitted (the default) is the unchanged Phase 2 behavior - the most recent session. The id is always re-scoped to this Mind, so it can only ever address a night this caller was already entitled to read.

TOS-2777 Gate C: the report's learning_narrative field carries real proposition/retrospect content, not status - narrower than this route's own chat-entitled gate, so it is independently withheld from a non-owner caller (see _learning_narrative_for_session).