Session resume: Hardcoded Pi config path

[yurikhan]

Pi accepts an environment variable, PI_CODING_AGENT_DIR, and looks for its configs, sessions, user-scoped skills, commands, prompt overrides, etc, down that directory.

Naturally, on my machine, that is set to ~/.config/pi/agent (so sessions are in ~/.config/pi/agent/sessions/*/*.jsonl).

However, pi-coding-agent--list-sessions hardcodes ~/.pi/agent/sessions/. As a consequence, it does not find any of my sessions.

I suggest one of the following:

1. read the same environment variable (defaulting to ~/.config/pi/agent) and expand sessions/ against the value, OR
2. have a Custom option that can be set by the user, OR
3. take an existing session’s sessionFile (from the get_state or get_session_stats) and strip the file name off that.

[dnouri]

@yurikhan Thanks for the report. This has been fixed in #206 via your third suggestion.