feat(obs): add metrics runtime controller status (#3408)

docs/architecture/background-services-inventory.md

@@ -47,7 +47,7 @@ not define a new scheduler, controller framework, or shutdown contract.
 | Notification runtime | `rustfs/src/server/event.rs::init_event_notifier` initializes live event stream support even when notification targets are disabled; when enabled, it loads server config and activates targets. Config reload uses `NotificationConfigManager::reload_config`. | Installs ECStore event dispatch hook, activates notification targets, manages replay/runtime target state, and supports live event streams. | Notification module state is refreshed from persisted module switches; target health is available through runtime target status. | Keep live event stream support separate from target delivery enablement. Reload must remain admin-triggered and peer-signaled. |
 | Audit runtime | `rustfs/src/server/audit.rs::start_audit_system` starts audit only when module switches and configured targets allow it. `AuditSystem::reload_config` replaces runtime targets. | Dispatches audit events to configured targets and manages replay workers. | Audit observability records config reloads and target delivery metrics. | Do not couple audit lifecycle to notification lifecycle even though the runtime patterns are similar. |
 | Dynamic config reload | Admin config handlers call `apply_dynamic_config_for_subsystem`, then `signal_dynamic_config_reload` or `signal_config_snapshot_reload` through the global notification system. | Applies scanner/heal runtime config, audit reloads, notification reloads, and peer reload signals. | Logs local and peer reload failures. Audit reload increments audit config reload metrics. | This is admin-triggered fanout, not a background scheduler. Controller work should preserve per-subsystem validation and error boundaries. |
-| Metrics runtime | `crates/obs/src/metrics/scheduler.rs::init_metrics_runtime` spawns multiple interval loops for cluster, bucket, node, resource, audit, notification, and replication bandwidth metrics. | Periodically collects and reports metrics. | Reports through the metrics runtime and logs cancellation warnings. | Keep intervals and collector grouping stable while adding status snapshots. |
+| Metrics runtime | `crates/obs/src/metrics/scheduler.rs::init_metrics_runtime` spawns multiple interval loops for cluster, bucket, node, resource, audit, notification, and replication bandwidth metrics. | Periodically collects and reports metrics. | Reports through the metrics runtime, logs cancellation warnings, and exposes a typed read-only status snapshot plus a no-op reconcile plan for enablement, collector task count, intervals, replication bandwidth tombstone cycles, cancellation source, and shutdown handle shape. | Keep intervals and collector grouping stable. The current controller surface does not mutate workers. |
 | Memory observability | `rustfs/src/memory_observability.rs::init_memory_observability` spawns a token-cancelled sampler. | Periodically records memory snapshots. | Emits memory observability metrics and exposes a read-only status snapshot plus a no-op reconcile plan for metrics enablement, interval, cancellation source, and shutdown handle shape. | This is the first low-risk pilot for controller status because it already has a simple token loop and the pilot does not mutate workers. |
 | Allocator reclaim | `rustfs/src/allocator_reclaim.rs::init_allocator_reclaim` spawns a token-cancelled reclaim loop when enabled. | Observes reclaimable work and may run allocator reclaim after idle intervals. | Emits reclaim enabled/backend counters, active-request gauges, scanner/heal activity gauges, and reclaim result counters. Exposes a typed read-only status snapshot plus a no-op reconcile plan for enablement, backend, effective force, intervals, cancellation source, and shutdown handle shape. | A controller must preserve idle-streak logic and backend-specific force behavior. The current controller surface does not mutate workers. |
 | Auto-tuner | `rustfs/src/init.rs::init_auto_tuner` optionally spawns a 60-second loop when `RUSTFS_AUTOTUNER_ENABLED` is true. | Tunes concurrency manager settings from performance metrics. | Logs iteration success/failure. | Treat as behavior-sensitive; a future controller needs explicit rollback because it can change runtime concurrency. |