SIENTIAPDE-1973

SIENTIAPDE-1973: Implement per-connector OPC client certificates and remove legacy read engine.
This update overhauls certificate management, transitioning from a single platform certificate to individual client certificates defined in the slot configuration. The CertProvider now downloads certificates from MinIO based on certificate_id, applying dynamic security policies (mode, policy) from the slot. The legacy READ_ENGINE=legacy option and OpcManager have been entirely removed, standardizing on the ServerReader with strict slot v2 enforcement. Write command resolution (ServerConfigResolver) now consistently uses connectors joined with opc_certificates. The CERT_BUCKET environment variable is no longer used.

CLAUDE.md

@@ -41,7 +41,6 @@ app.py (asyncio loop, signals, Prometheus server)
        -> IngestorManager (managers/ingestor_manager.py) — central coordinator
             -> ResourceManager (managers/resource_manager.py) — Redis slot leases, heartbeats, active-ingestor registry
             -> ServerReader (managers/server_reader.py), one per OPC server — SubscriptionEngine over the shared OpcConnectionPool
-               (READ_ENGINE=legacy: OpcManager (managers/opc_manager.py), the rc3 reader kept as plan B until the end of SIENTIAPDE-1974)
             -> OpcConnectionPool (connection/pool.py) + CertProvider (connection/certs.py) — pooled connections, cert from MinIO
             -> DataManager (managers/data_manager.py) — MongoDB persistence + optional Kafka publish
 ```
@@ -58,9 +57,9 @@ app.py (asyncio loop, signals, Prometheus server)
 
 Any change to slot/lease counts should be traced through `manage_leases`/`manage_no_slots` — that's where the rebalancing math lives, not in `ResourceManager` itself (which just does Redis primitives).
 
-**ServerReader** (SIENTIAPDE-1974, default `READ_ENGINE=v2`; the legacy `OpcManager` stays as plan B with `READ_ENGINE=legacy` — slot v1 only, certificate files from the Gitea clone — until it is unused and the tests pass the same without it) reads one OPC server through a `SubscriptionEngine`: the connection comes from the shared `OpcConnectionPool` (also used by NATS writes and gRPC), which fetches the platform certificate from MinIO via `CertProvider` and uses `SecurityPolicyBasic256Sha256` — no certificate files in the repo/image. Slots are parsed by `io/slots.py` (`parse_slot`), which accepts slot v2 (`names[]`) and converts the legacy v1 (`topics`). `datachange_notification` fans each value out to every `names` entry via `DataSink`. Subscribed connections are pinned in the pool so the idle sweep never drops them. Tracks `non_receive_count` to detect silently-dead subscriptions (`check_cycles` / `check_opc_listenning`); a lost server is shut down (pool connection evicted) and re-initialized on the next loop.
+**ServerReader** (SIENTIAPDE-1974) reads one OPC server through a `SubscriptionEngine`: the connection comes from the shared `OpcConnectionPool` (also used by NATS writes and gRPC). Slots are slot v2 only, parsed by `io/slots.py` (`parse_slot`): each server carries `security` (`mode`, `policy`) and `certificate` (certificate_id, application_uri, MinIO `bucket`/`object_name` of cert and private_key, from `opc_certificates` via the Orchestrator; `None` = connect without security, D5). The pool applies security only with a certificate (`connection/security.py`: `is_secured`, `apply_security` maps mode/policy to asyncua, unknown → error), and `CertProvider` downloads each certificate into `<CERT_CACHE_DIR>/<certificate_id>/` (cache, lock and `invalidate` per certificate) — no certificate files in the repo/image, no default certificate. A change of `security`/`certificate` in the slot re-initializes the reader (pool connection evicted). `datachange_notification` fans each value out to every `names` entry via `DataSink`. Subscribed connections are pinned in the pool so the idle sweep never drops them. Tracks `non_receive_count` to detect silently-dead subscriptions (`check_cycles` / `check_opc_listenning`); a lost server is shut down (pool connection evicted) and re-initialized on the next loop.
 
-**Writes** (SIENTIAPDE-1975): `NatsWriteConsumer` → `WriteEngine` → pool, then `DataSink.update_write_status`. Commands (C2) carry only `server_id`; `ServerConfigResolver` (`connection/servers.py`) resolves the connection (command override → live pooled connection → `connectors` → `opc-servers`). `write_status` keeps the worst outcome (`ok` < `error` < `session_bad`); the gateway is the only one that updates it (the Laborious inserts the row as `pending` and never records OPC outcomes). The NATS first connect is bounded (it runs on the main loop); reconnection after it is unbounded.
+**Writes** (SIENTIAPDE-1975): `NatsWriteConsumer` → `WriteEngine` → pool, then `DataSink.update_write_status`. Commands (C2) carry only `server_id`; `ServerConfigResolver` (`connection/servers.py`) resolves the connection: live pooled connection → `connectors` aggregation with a `$lookup` on `opc_certificates`, in the slot format. The certificate rule (active + client, `connection/certificates.py`) mirrors the Orchestrator's `tag_database.resolve_certificate` — keep both in sync (SIENTIAPDE-1974 D1; the Mongo fallback goes away when writes are routed to the pod that owns the connection). `write_status` keeps the worst outcome (`ok` < `error` < `session_bad`); the gateway is the only one that updates it (the Laborious inserts the row as `pending` and never records OPC outcomes). The NATS first connect is bounded (it runs on the main loop); reconnection after it is unbounded.
 
 **Metrics** (`ingestor/metrics.py`): all Prometheus metrics defined here, always labeled by `pod_id`. Emitted via `SientiaMonitoring.emit_metric(...)` (from `sientia_do`), not the prometheus client directly — new metrics should follow that pattern for consistency with logging/notifications.