- sessions.el: add session_exists() for chat-path session validation (ISSUE #6/#7)
- sessions.el: add session_create_cleanup() for ghost-session rollback (ISSUE #1)
- sessions.el: set session_pending_first_msg flag in session_create; clear it in
session_hist_save so the first successful chat marks the session active (ISSUE #1)
- sessions.el: session_delete now clears mcp_bridge:<id> and always_allow_<id>
state keys so abandoned pending-tool sessions do not accumulate (ISSUE #5)
- sessions.el: add TODO comments for ISSUE #2 (no TTL/expiry), ISSUE #3
(non-atomic delete-then-create), ISSUE #4 (no concurrent-create guard),
and ISSUE #8 (reconnect/duplicate resume race) where fixes are too invasive
to land without new runtime primitives
- chat.el: validate session_id exists via session_exists() before entering
agentic_loop; unknown session_ids now return a 404-style error instead of
silently starting a fresh empty session (ISSUE #6/#7)
will.anderson