Add CleanupOrphanedSessions() function that runs at `gt start` time to
detect and kill zombie tmux sessions (sessions where tmux is alive but
the Claude process has died).
This prevents:
- Session name conflicts when restarting agents
- Resource accumulation from orphaned sessions
- Process accumulation that can overwhelm the system
The function scans for sessions with `gt-*` and `hq-*` prefixes, checks
if Claude is running using IsClaudeRunning(), and kills zombie sessions
using KillSessionWithProcesses() for proper cleanup.
Fixes#700
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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