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-flow/trustgraph/metering/counter.py

@@ -50,30 +50,37 @@ class Processor(FlowProcessor):
             )
         )
 
+        # Per-workspace price tables
         self.prices = {}
 
         self.config_key = "token-cost"
 
-    # Load token costs from the config service
-    async def on_cost_config(self, config, version):
+    async def on_cost_config(self, workspace, config, version):
 
-        logger.info(f"Loading metering configuration version {version}")
+        logger.info(
+            f"Loading metering configuration version {version} "
+            f"for workspace {workspace}"
+        )
 
         if self.config_key not in config:
-            logger.warning(f"No key {self.config_key} in config")
+            logger.warning(
+                f"No key {self.config_key} in config for {workspace}"
+            )
+            self.prices[workspace] = {}
             return
 
-        config = config[self.config_key]
+        prices = config[self.config_key]
 
-        self.prices = {
+        self.prices[workspace] = {
             k: json.loads(v)
-            for k, v in config.items()
+            for k, v in prices.items()
         }
 
-    def get_prices(self, modelname):
+    def get_prices(self, workspace, modelname):
 
-        if modelname in self.prices:
-            model = self.prices[modelname]
+        ws_prices = self.prices.get(workspace, {})
+        if modelname in ws_prices:
+            model = ws_prices[modelname]
             return model["input_price"], model["output_price"]
         return None, None  # Return None if model is not found
 
@@ -81,6 +88,8 @@ class Processor(FlowProcessor):
 
         v = msg.value()
 
+        workspace = flow.workspace
+
         modelname = v.model or "unknown"
         num_in = v.in_token or 0
         num_out = v.out_token or 0
@@ -89,7 +98,9 @@ class Processor(FlowProcessor):
         __class__.token_metric.labels(model=modelname, direction="input").inc(num_in)
         __class__.token_metric.labels(model=modelname, direction="output").inc(num_out)
 
-        model_input_price, model_output_price = self.get_prices(modelname)
+        model_input_price, model_output_price = self.get_prices(
+            workspace, modelname
+        )
 
         if model_input_price == None:
             cost_per_call = f"Model Not Found in Price list"