* fix(agent-claude-code): return idle state when no JSONL session file exists
Freshly spawned sessions had no Claude Code JSONL file yet (Claude Code
doesn't create it until the first conversation), causing getActivityState
to return null → displayed as 'unknown' in ao status.
When the process is running but no session file exists, return
{ state: 'idle', timestamp: now } so the dashboard shows the correct
state immediately after spawn.
Closes#883
* fix(agent-claude-code): use session.createdAt for idle timestamp when no JSONL file
Using new Date() as the timestamp caused isIdleBeyondThreshold to always
compute ~0ms, preventing stuck detection from ever firing for sessions that
hang before creating a JSONL file. Using session.createdAt correctly
represents when the session began, allowing stuck detection to eventually
trigger.
be0ce0baac