Establish session persistence and mediation (mediate-session)

[Copilot]

Sessions had no file-based persistence — mediate_session only wrote to AtomSpace (when available), and resume_session had no fallback for cross-process recovery. The Scheme module also shadowed the C++ SessionManager bindings with weaker pure-Scheme wrappers and omitted key exports.

C++ (SessionManager)

• File persistence: persist_session_to_file() serialises metadata + full message history to ~/.caichat/sessions/<name>.json; load_session_from_file() deserialises and populates restored_messages for replay into the restored ChatCompletion
• resume_session(): now checks memory → AtomSpace → file before creating a new session; replays messages back into the live completion instance
• mediate_session(): always persists (previously skipped active sessions, leaving their state unwritten)
• persist_session(): uses a new session_id_to_name_ reverse map for O(1) name lookup instead of linear scan
• get_session_file_path(): creates ~/.caichat/sessions/ tree with errno-aware error reporting
• Bidirectional session_name_to_id_ / session_id_to_name_ maps maintained across all session lifecycle calls

Scheme

• caichat.scm: exports caichat-create-persistent-session, caichat-resume-session, caichat-mediate-session, caichat-audit-core-modules, caichat-neural-symbolic-bridge; removes Scheme wrappers that shadowed the C++ bindings
• init.scm: re-exports caichat-create-persistent-session and caichat-resume-session
• repl.scm: adds /persist <name>, /resume <name>, /mediate interactive commands and updates help text

;; Create a named persistent session — saved immediately to ~/.caichat/sessions/my-session.json
(define sid (caichat-create-persistent-session "my-session" "openai" "gpt-4"))

;; Sync state to disk at any point during the session
(caichat-mediate-session sid)

;; Resume across processes — loads from file when not in memory/AtomSpace
(define sid2 (caichat-resume-session "my-session" "openai" "gpt-4"))

Original prompt

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This section details on the original issue you should resolve

<issue_title>Establish session persistence and mediation (mediate-session)</issue_title>
<issue_description></issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Establish session persistence and mediation (mediate-session) #15

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[drzo]

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