Adds coordinator.fleetMetrics() computing queue depth, stage histogram,
oldest-queued age (starvation signal), factory health and seat utilization,
plus derived alerts (no_live_capacity, all_factories_down, queue_starvation,
saturated, stale_factories). Exposed via GET /fleet/metrics and surfaced as a
metrics+alerts panel on the fleet overview. Thresholds injectable for tests.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
New e2e/fleet.spec.ts with a method- and URL-aware /api/fleet/** mock that
holds mutable state so operator actions and budget toggles reflect in
follow-up GETs. Covers: fleet overview (factory cards + recent jobs), jobs
table + stage filter, job detail requeue (stage building->queued) with the
SSE-driven Live badge, and budget pause/resume. All 4 specs green.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
