feat: workspace-based multi-tenancy, replacing user as tenancy axis (#840)

Introduces `workspace` as the isolation boundary for config, flows,
library, and knowledge data. Removes `user` as a schema-level field
throughout the code, API specs, and tests; workspace provides the
same separation more cleanly at the trusted flow.workspace layer
rather than through client-supplied message fields.

Design
------
- IAM tech spec (docs/tech-specs/iam.md) documents current state,
  proposed auth/access model, and migration direction.
- Data ownership model (docs/tech-specs/data-ownership-model.md)
  captures the workspace/collection/flow hierarchy.

Schema + messaging
------------------
- Drop `user` field from AgentRequest/Step, GraphRagQuery,
  DocumentRagQuery, Triples/Graph/Document/Row EmbeddingsRequest,
  Sparql/Rows/Structured QueryRequest, ToolServiceRequest.
- Keep collection/workspace routing via flow.workspace at the
  service layer.
- Translators updated to not serialise/deserialise user.

API specs
---------
- OpenAPI schemas and path examples cleaned of user fields.
- Websocket async-api messages updated.
- Removed the unused parameters/User.yaml.

Services + base
---------------
- Librarian, collection manager, knowledge, config: all operations
  scoped by workspace. Config client API takes workspace as first
  positional arg.
- `flow.workspace` set at flow start time by the infrastructure;
  no longer pass-through from clients.
- Tool service drops user-personalisation passthrough.

CLI + SDK
---------
- tg-init-workspace and workspace-aware import/export.
- All tg-* commands drop user args; accept --workspace.
- Python API/SDK (flow, socket_client, async_*, explainability,
  library) drop user kwargs from every method signature.

MCP server
----------
- All tool endpoints drop user parameters; socket_manager no longer
  keyed per user.

Flow service
------------
- Closure-based topic cleanup on flow stop: only delete topics
  whose blueprint template was parameterised AND no remaining
  live flow (across all workspaces) still resolves to that topic.
  Three scopes fall out naturally from template analysis:
    * {id} -> per-flow, deleted on stop
    * {blueprint} -> per-blueprint, kept while any flow of the
      same blueprint exists
    * {workspace} -> per-workspace, kept while any flow in the
      workspace exists
    * literal -> global, never deleted (e.g. tg.request.librarian)
  Fixes a bug where stopping a flow silently destroyed the global
  librarian exchange, wedging all library operations until manual
  restart.

RabbitMQ backend
----------------
- heartbeat=60, blocked_connection_timeout=300. Catches silently
  dead connections (broker restart, orphaned channels, network
  partitions) within ~2 heartbeat windows, so the consumer
  reconnects and re-binds its queue rather than sitting forever
  on a zombie connection.

Tests
-----
- Full test refresh: unit, integration, contract, provenance.
- Dropped user-field assertions and constructor kwargs across
  ~100 test files.
- Renamed user-collection isolation tests to workspace-collection.

trustgraph-cli/trustgraph/cli/get_document_content.py

@@ -9,21 +9,19 @@ from trustgraph.api import Api
 
 default_url = os.getenv("TRUSTGRAPH_URL", 'http://localhost:8088/')
 default_token = os.getenv("TRUSTGRAPH_TOKEN", None)
-default_user = "trustgraph"
+default_workspace = os.getenv("TRUSTGRAPH_WORKSPACE", "default")
 
-def get_content(url, user, document_id, output_file, token=None):
+def get_content(url, document_id, output_file, token=None, workspace="default"):
 
-    api = Api(url, token=token).library()
+    api = Api(url, token=token, workspace=workspace).library()
 
-    content = api.get_document_content(user=user, id=document_id)
+    content = api.get_document_content(id=document_id)
 
     if output_file:
         with open(output_file, 'wb') as f:
             f.write(content)
         print(f"Written {len(content)} bytes to {output_file}")
     else:
-        # Write to stdout
-        # Try to decode as text, fall back to binary info
         try:
             text = content.decode('utf-8')
             print(text)
@@ -51,9 +49,9 @@ def main():
     )
 
     parser.add_argument(
-        '-U', '--user',
-        default=default_user,
-        help=f'User ID (default: {default_user})'
+        '-w', '--workspace',
+        default=default_workspace,
+        help=f'Workspace (default: {default_workspace})',
     )
 
     parser.add_argument(
@@ -73,10 +71,10 @@ def main():
 
         get_content(
             url=args.api_url,
-            user=args.user,
             document_id=args.document_id,
             output_file=args.output,
             token=args.token,
+            workspace=args.workspace,
         )
 
     except Exception as e: