The ACP prompt path called set_session_vars(session_key=session_id, ...)
without passing session_id, so the HERMES_SESSION_ID ContextVar was bound
to its explicit "" default. Once the session-context machinery is engaged,
_inject_session_context_env treats an explicitly-bound "" as authoritative
and writes it to the child env — so subprocesses spawned during an ACP turn
got an empty HERMES_SESSION_ID instead of the session's own id.
Pass session_id through so child subprocesses carry the correct id.
Salvage of the ACP half of #53454 by @necoweb3 (the V4A-path half is
salvaged separately in the file-tools PR).
Co-authored-by: necoweb3 <sswdarius@gmail.com>
a5f94e93ad