feat: pluggable bootstrap framework with ordered initialisers (#847)

A generic, long-running bootstrap processor that converges a
deployment to its configured initial state and then idles.
Replaces the previous one-shot `tg-init-trustgraph` container model
and provides an extension point for enterprise / third-party
initialisers.

See docs/tech-specs/bootstrap.md for the full design.

Bootstrapper
------------
A single AsyncProcessor (trustgraph.bootstrap.bootstrapper.Processor)
that:

  * Reads a list of initialiser specifications (class, name, flag,
    params) from either a direct `initialisers` parameter
    (processor-group embedding) or a YAML/JSON file (`-c`, CLI).
  * On each wake, runs a cheap service-gate (config-svc +
    flow-svc round-trips), then iterates the initialiser list,
    running each whose configured flag differs from the one stored
    in __system__/init-state/<name>.
  * Stores per-initialiser completion state in the reserved
    __system__ workspace.
  * Adapts cadence: ~5s on gate failure, ~15s while converging,
    ~300s in steady state.
  * Isolates failures — one initialiser's exception does not block
    others in the same cycle; the failed one retries next wake.

Initialiser contract
--------------------
  * Subclass trustgraph.bootstrap.base.Initialiser.
  * Implement async run(ctx, old_flag, new_flag).
  * Opt out of the service gate with class attr
    wait_for_services=False (only used by PulsarTopology, since
    config-svc cannot come up until Pulsar namespaces exist).
  * ctx carries short-lived config and flow-svc clients plus a
    scoped logger.

Core initialisers (trustgraph.bootstrap.initialisers.*)
-------------------------------------------------------
  * PulsarTopology   — creates Pulsar tenant + namespaces
                       (pre-gate, blocking HTTP offloaded to
                        executor).
  * TemplateSeed     — seeds __template__ from an external JSON
                       file; re-run is upsert-missing by default,
                       overwrite-all opt-in.
  * WorkspaceInit    — populates a named workspace from either
                       the full contents of __template__ or a
                       seed file; raises cleanly if the template
                       isn't seeded yet so the bootstrapper retries
                       on the next cycle.
  * DefaultFlowStart — starts a specific flow in a workspace;
                       no-ops if the flow is already running.

Enterprise or third-party initialisers plug in via fully-qualified
dotted class paths in the bootstrapper's configuration — no core
code change required.

Config service
--------------
  * push(): filter out reserved workspaces (ids starting with "_")
    from the change notifications.  Stored config is preserved; only
    the broadcast is suppressed, so bootstrap / template state lives
    in config-svc without live processors ever reacting to it.

Config client
-------------
  * ConfigClient.get_all(workspace): wraps the existing `config`
    operation to return {type: {key: value}} for a workspace.
    WorkspaceInit uses it to copy __template__ without needing a
    hardcoded types list.

pyproject.toml
--------------
  * Adds a `bootstrap` console script pointing at the new Processor.

* Remove tg-init-trustgraph, superceded by bootstrap processor

trustgraph-base/trustgraph/base/config_client.py

@@ -84,6 +84,18 @@ class ConfigClient(RequestResponse):
         )
         return resp.directory
 
+    async def get_all(self, workspace, timeout=CONFIG_TIMEOUT):
+        """Return every config entry in ``workspace`` as a nested dict
+        ``{type: {key: value}}``.  Values are returned as the raw
+        strings stored by config-svc (typically JSON); callers parse
+        as needed.  An empty dict means the workspace has no config."""
+        resp = await self._request(
+            operation="config",
+            workspace=workspace,
+            timeout=timeout,
+        )
+        return resp.config
+
     async def workspaces_for_type(self, type, timeout=CONFIG_TIMEOUT):
         """Return the set of distinct workspaces with any config of
         the given type."""