* fix(server): fail agents when provider process exits
The transport previously closed pending RPCs without terminating the active manager run, leaving the agent stuck in running state. Propagate unexpected process termination as a one-shot turn failure while suppressing it during intentional session close.
* fix(server): keep idle provider exits recoverable
A process death with no active foreground turn is not a failed turn and must not trigger turn-based lifecycle actions. Leave the session disconnected so the next prompt reconnects without publishing a false terminal event.
* fix(server): preserve provider exit recovery
Connection cleanup after a failed reconnect must not close the durable session boundary or discard AgentManager subscribers. Treat both foreground and autonomous root turns as active when propagating process death.
* test(server): make process exit harness portable
* fix(server): clear permissions after provider exit
* fix(server): preserve plan approval after provider exit
* fix(server): serialize provider reconnects
* fix(server): stop reconnects after session close
