frontend: surface the new automation `reliability` field (full vs sse-only)

Follow-up from #44 (feat: add activitylog-based reconciliation backstop for event triggers).

GET /me/automation (model.AutomationStatus) now returns a reliability field: "full" when the last reconciliation attempt for a user succeeded (or none was needed yet), "sse-only" when it errored (activitylog unreachable/disabled, or a non-200 response). This is currently backend-only — nothing in the frontend reads or surfaces it.

Per the design spec (docs/superpowers/specs/2026-08-20-event-trigger-reliability-design.md, "Degradation visibility"), the intended UX is for WorkflowList.vue to surface this the same way it already surfaces automation connection state (see docs/superpowers/specs/2026-07-24-automation-connect-ux-design.md for the existing pattern) — a status line change, not a new panel: something like "Background execution active" for "full" vs. a distinguishable degraded state for "sse-only".

This was scoped out of #44 as backend-only with no UI surface, left for this follow-up.

Start with WorkflowList.vue and the existing automation connection-state status pattern described in docs/superpowers/specs/2026-07-24-automation-connect-ux-design.md. Read the degradation visibility section of docs/superpowers/specs/2026-08-20-event-trigger-reliability-design.md and inspect GET /me/automation for the reliability value. Done means the status line distinguishes full background execution from the degraded sse-only state.