b9b804eac5
Extend SenseComputeReturn to support shell triggers in addition to workflow
triggers via a discriminated union (kind: 'shell' | 'workflow').
Shell triggers execute a command string in the sense worker subprocess
(spawned detached). The kernel logs 'shell-launch' events without involving
the workflow manager.
Breaking change: WorkflowTrigger now requires kind: 'workflow'.
New ShellTrigger type: { kind: 'shell', command: string }.
SenseTrigger = WorkflowTrigger | ShellTrigger.
Closes #315