Session manager

The session manager orchestrates the full lifecycle of a cognitive session from first event to final cleanup. At session creation, it allocates a new session ID, loads the relevant identity state and policy snapshot from PostgreSQL, hydrates working memory with any high-priority items flagged from previous sessions, and registers the participating agent instances. Between turns within a session, it persists the working memory state so that context from earlier in the conversation influences retrieval and deliberation in later turns - without this persistence, each turn would be processed in complete isolation. At session close, it flushes the accumulated working memory state, records the final policy drift delta against the opening snapshot, packages the session's experience events for the consolidation pipeline, and updates the session metadata in PostgreSQL. The session manager also handles interruptions: if a session is terminated unexpectedly, it attempts a best-effort state flush and marks the session as interrupted in the audit stream so that partial state is not silently lost.