SIENTIAPDE-1974: feat(read): slot v2 reads via SubscriptionEngine, OPC cert from MinIO

Swaps the legacy OpcManager read path for the gateway's SubscriptionEngine over
the shared OpcConnectionPool. The OPC client certificate now always comes from
MinIO + Mongo (CertProvider, Basic256Sha256) — no more certs/ shipped in the
Gitea repository, so a new version branch no longer breaks the reads.

- io/slots.py: parse_slot accepts slot v2 (names[]) and converts the legacy
  v1 (tag_name + topics; cert_path => use_security, path dropped), so gateway
  and Orchestrator can be deployed in any order.
- managers/server_reader.py: new per-server reader with the OpcManager
  interface the IngestorManager already drives (connect, create_subscription,
  subscribe, unsubscribe, check_cycles, check_opc_listenning, shutdown).
- IngestorManager owns the read path: lazy-MinIO CertProvider, the pool and a
  read DataSink, built without touching the network. Slots from Redis are
  normalized on lease and refresh; a malformed slot is notified and the last
  good config is kept.
- GatewayRuntime borrows the pool (writes/gRPC) instead of building it, and no
  longer closes it on stop: a Postgres/NATS failure can't stop the reads.
- pool: pin/unpin per active subscription so release_idle never evicts a
  subscribed connection; public evict() for lost servers / changed config.
- SubscriptionEngine pins on subscribe, unpins on unsubscribe, and drops a
  subscription locally even when the server-side delete fails.
- DataSink: model_id only written when the name has one, keeping v1 documents
  identical to the legacy ones.
- config: CERT_BUCKET default is the legacy streamlit-connectors bucket (D7).
- Removes OpcManager, its tests and scripts/generate-and-push-opc-cert.sh;
  README/CLAUDE.md document the MinIO certificate and the slot v2 format.

Tests: 218 unit tests pass; ruff check/format clean. Local end-to-end against
an asyncua server: v1 slot with two topics -> one doc per collection, legacy
doc shape, idle sweep keeps the subscription, lost-server shutdown and
re-initialization work.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/unit/io/test_data_sink_publish.py

@@ -67,3 +67,26 @@ async def test_publish_reading_emits_tag_value_metric_per_name():
         value=42,
         tags={'pod_id': dm.pod_id, 'tag_name': 'Counter', 'model_id': '1'},
     )
+
+
+@pytest.mark.asyncio
+async def test_publish_reading_without_model_id_keeps_legacy_doc():
+    """Names converted from a slot v1 carry no model_id: the document must be the
+    same as the legacy OpcManager one (SIENTIAPDE-1974 NF2)."""
+    sink, dm = make_sink()
+    names = [{'collection': 'raw_x', 'tag_name': 'Counter'}]
+
+    await sink.publish_reading(
+        tag='ns=2;i=2', value=42, timestamp='2026-07-13 00:00:00+0000', names=names
+    )
+
+    collection, doc = dm.publish.await_args_list[0].args
+    assert collection == 'raw_x'
+    assert doc == {
+        'tag': 'ns=2;i=2',
+        'name': 'Counter',
+        'timestamp': '2026-07-13 00:00:00+0000',
+        'value': 42,
+    }
+    _, kwargs = sink.emit_metric.await_args
+    assert kwargs['tags']['model_id'] == ''

tests/unit/io/test_slots.py

@@ -62,3 +62,102 @@ def test_parse_slot_rejects_tag_without_names():
 
     with pytest.raises((KeyError, ValueError)):
         parse_slot(raw)
+
+
+RAW_V1 = {
+    'kepserver': {
+        'name': 'kepserver',
+        'server_id': '1',
+        'url': 'opc.tcp://kepserver:49320',
+        'server_uri': 'urn:sientia:opc-ingestor',
+        'cert_path': '/app/certs/opc-ingestor-cert.pem',
+        'private_key_path': '/app/certs/opc-ingestor-key.pem',
+        'server_cert_path': None,
+        'subscription_period_ms': 15000.0,
+        'tags': {
+            'ns=2;s=A.TargetSin': {
+                'aggr_func': 'lts',
+                'frequency': 30000,
+                'server_id': '1',
+                'tag_address': 'ns=2;s=A.TargetSin',
+                'tag_name': 'TargetSin',
+                'topics': ['raw_scouter-sin-approx', 'raw_other-model'],
+            }
+        },
+    }
+}
+
+
+def test_parse_slot_converts_v1_topics_to_names():
+    """Slot v1 (current Orchestrator) is read as v2: one name per topic, no model_id,
+    so the documents stay identical to the legacy ones (SIENTIAPDE-1974 G1)."""
+    server = parse_slot(RAW_V1)['kepserver']
+    tag = server['tags']['ns=2;s=A.TargetSin']
+
+    assert tag['names'] == [
+        {'collection': 'raw_scouter-sin-approx', 'tag_name': 'TargetSin'},
+        {'collection': 'raw_other-model', 'tag_name': 'TargetSin'},
+    ]
+    assert tag['frequency'] == 30000
+    assert tag['active_read'] == {'enabled': False}
+
+
+def test_parse_slot_v1_cert_path_means_security_but_path_is_dropped():
+    server = parse_slot(RAW_V1)['kepserver']
+
+    assert server['use_security'] is True
+    assert server['name'] == 'kepserver'
+    assert server['server_id'] == '1'
+    assert server['subscription_period_ms'] == 15000.0
+    # the certificate always comes from MinIO now: no file path survives the parse
+    assert 'cert_path' not in server
+    assert 'private_key_path' not in server
+
+
+def test_parse_slot_v1_without_cert_path_is_insecure():
+    raw = {
+        's': {
+            'server_id': '2',
+            'url': 'u',
+            'cert_path': None,
+            'tags': {'ns=2;i=1': {'tag_name': 't', 'frequency': '1000', 'topics': ['raw_c']}},
+        }
+    }
+
+    server = parse_slot(raw)['s']
+
+    assert server['use_security'] is False
+    assert server['name'] == 's'  # falls back to the slot key
+
+
+def test_parse_slot_v2_explicit_use_security_wins():
+    raw = {
+        's': {
+            'server_id': '1',
+            'url': 'u',
+            'use_security': False,
+            'cert_path': '/legacy/path',
+            'tags': {
+                'ns=2;i=1': {
+                    'frequency': '1000',
+                    'names': [{'collection': 'c', 'tag_name': 't', 'model_id': '1'}],
+                }
+            },
+        }
+    }
+
+    assert parse_slot(raw)['s']['use_security'] is False
+
+
+def test_parse_slot_rejects_v1_tag_without_tag_name():
+    raw = {
+        's': {
+            'server_id': '1',
+            'url': 'u',
+            'tags': {'ns=2;i=1': {'frequency': '1', 'topics': ['c']}},
+        }
+    }
+    import pytest
+
+    with pytest.raises(ValueError):
+        parse_slot(raw)