Pub/sub abstraction: decouple from Pulsar (#751)

Remove Pulsar-specific concepts from application code so that
the pub/sub backend is swappable via configuration.

Rename translators:
- to_pulsar/from_pulsar → decode/encode across all translator
  classes, dispatch handlers, and tests (55+ files)
- from_response_with_completion → encode_with_completion
- Remove pulsar.schema.Record from translator base class

Queue naming (CLASS:TOPICSPACE:TOPIC):
- Replace topic() helper with queue() using new format:
  flow:tg:name, request:tg:name, response:tg:name, state:tg:name
- Queue class implies persistence/TTL (no QoS in names)
- Update Pulsar backend map_topic() to parse new format
- Librarian queues use flow class (persistent, for chunking)
- Config push uses state class (persistent, last-value)
- Remove 15 dead topic imports from schema files
- Update init_trustgraph.py namespace: config → state

Confine Pulsar to pulsar_backend.py:
- Delete legacy PulsarClient class from pubsub.py
- Move add_args to add_pubsub_args() with standalone flag
  for CLI tools (defaults to localhost)
- PulsarBackendConsumer.receive() catches _pulsar.Timeout,
  raises standard TimeoutError
- Remove Pulsar imports from: async_processor, flow_processor,
  log_level, all 11 client files, 4 storage writers, gateway
  service, gateway config receiver
- Remove log_level/LoggerLevel from client API
- Rewrite tg-monitor-prompts to use backend abstraction
- Update tg-dump-queues to use add_pubsub_args

Also: pubsub-abstraction.md tech spec covering problem statement,
design goals, as-is requirements, candidate broker assessment,
approach, and implementation order.

tests/unit/test_pubsub/test_queue_naming.py

@@ -0,0 +1,133 @@
+"""
+Tests for queue naming and topic mapping.
+"""
+
+import pytest
+import argparse
+
+from trustgraph.schema.core.topic import queue
+from trustgraph.base.pubsub import get_pubsub, add_pubsub_args
+from trustgraph.base.pulsar_backend import PulsarBackend
+
+
+class TestQueueFunction:
+
+    def test_flow_default(self):
+        assert queue('text-completion-request') == 'flow:tg:text-completion-request'
+
+    def test_request_class(self):
+        assert queue('config', cls='request') == 'request:tg:config'
+
+    def test_response_class(self):
+        assert queue('config', cls='response') == 'response:tg:config'
+
+    def test_state_class(self):
+        assert queue('config', cls='state') == 'state:tg:config'
+
+    def test_custom_topicspace(self):
+        assert queue('config', cls='request', topicspace='prod') == 'request:prod:config'
+
+    def test_default_class_is_flow(self):
+        result = queue('something')
+        assert result.startswith('flow:')
+
+
+class TestPulsarMapTopic:
+
+    @pytest.fixture
+    def backend(self):
+        """Create a PulsarBackend without connecting."""
+        b = object.__new__(PulsarBackend)
+        return b
+
+    def test_flow_maps_to_persistent(self, backend):
+        assert backend.map_topic('flow:tg:text-completion-request') == \
+            'persistent://tg/flow/text-completion-request'
+
+    def test_state_maps_to_persistent(self, backend):
+        assert backend.map_topic('state:tg:config') == \
+            'persistent://tg/state/config'
+
+    def test_request_maps_to_non_persistent(self, backend):
+        assert backend.map_topic('request:tg:config') == \
+            'non-persistent://tg/request/config'
+
+    def test_response_maps_to_non_persistent(self, backend):
+        assert backend.map_topic('response:tg:librarian') == \
+            'non-persistent://tg/response/librarian'
+
+    def test_passthrough_pulsar_uri(self, backend):
+        uri = 'persistent://tg/flow/something'
+        assert backend.map_topic(uri) == uri
+
+    def test_invalid_format_raises(self, backend):
+        with pytest.raises(ValueError, match="Invalid queue format"):
+            backend.map_topic('bad-format')
+
+    def test_invalid_class_raises(self, backend):
+        with pytest.raises(ValueError, match="Invalid queue class"):
+            backend.map_topic('unknown:tg:topic')
+
+    def test_custom_topicspace(self, backend):
+        assert backend.map_topic('flow:prod:my-queue') == \
+            'persistent://prod/flow/my-queue'
+
+
+class TestGetPubsubDispatch:
+
+    def test_unknown_backend_raises(self):
+        with pytest.raises(ValueError, match="Unknown pub/sub backend"):
+            get_pubsub(pubsub_backend='redis')
+
+
+class TestAddPubsubArgs:
+
+    def test_standalone_defaults_to_localhost(self):
+        parser = argparse.ArgumentParser()
+        add_pubsub_args(parser, standalone=True)
+        args = parser.parse_args([])
+        assert args.pulsar_host == 'pulsar://localhost:6650'
+        assert args.pulsar_listener == 'localhost'
+
+    def test_non_standalone_defaults_to_container(self):
+        parser = argparse.ArgumentParser()
+        add_pubsub_args(parser, standalone=False)
+        args = parser.parse_args([])
+        assert 'pulsar:6650' in args.pulsar_host
+        assert args.pulsar_listener is None
+
+    def test_cli_override_respected(self):
+        parser = argparse.ArgumentParser()
+        add_pubsub_args(parser, standalone=True)
+        args = parser.parse_args(['--pulsar-host', 'pulsar://custom:6650'])
+        assert args.pulsar_host == 'pulsar://custom:6650'
+
+    def test_pubsub_backend_default(self):
+        parser = argparse.ArgumentParser()
+        add_pubsub_args(parser)
+        args = parser.parse_args([])
+        assert args.pubsub_backend == 'pulsar'
+
+
+class TestQueueDefinitions:
+    """Verify the actual queue constants produce correct names."""
+
+    def test_config_request(self):
+        from trustgraph.schema.services.config import config_request_queue
+        assert config_request_queue == 'request:tg:config'
+
+    def test_config_response(self):
+        from trustgraph.schema.services.config import config_response_queue
+        assert config_response_queue == 'response:tg:config'
+
+    def test_config_push(self):
+        from trustgraph.schema.services.config import config_push_queue
+        assert config_push_queue == 'state:tg:config'
+
+    def test_librarian_request_is_persistent(self):
+        from trustgraph.schema.services.library import librarian_request_queue
+        assert librarian_request_queue.startswith('flow:')
+
+    def test_knowledge_request(self):
+        from trustgraph.schema.knowledge.knowledge import knowledge_request_queue
+        assert knowledge_request_queue == 'request:tg:knowledge'