Moved all 9P FUSE mount code from core to 9p module using lifecycle hooks.
Changes:
- Removed 9P-specific fields (mountProc, mountPath, mountEnabled) from execute.Server
- Removed WithMount(), MountPath(), startMount(), remountIfStale() functions
- Added lifecycle hooks: OnPreDispatch, OnClose, OnEnvSet with corresponding options
- Updated SetEnv(), Close(), and Dispatch() to call hooks instead of hardcoded mount logic
- Fixed tool descriptions to use $OLLIE_TOOLS_PATH instead of 9P-specific $OLLIE/s/$SID/t paths
- Removed unused execute import from agent/commands.go
The core execute server is now harness-agnostic.
fd20070294