refactor(operation-trace): isolate subsystem, fix install identity, merge migrations

- Move the operation-traceability service and its HTTP routes into a standalone
  pkg/operation_trace package; the Core controller package no longer depends on it
  (routes stay auto-discovered by the controller package scan).
- Gate the hot path on one module-level boolean exposed as ap.operation_trace_active:
  while no Workspace has tracing enabled the route wrapper performs zero trace work
  and zero database round trips. The gate opens when a Workspace enables tracing and
  is primed once at startup for already-enabled Workspaces.
- Record the installed extension identity for GitHub / marketplace / local / upload
  installs (owner/repo, author/name, filename) so the trace no longer shows a
  nameless "a plugin was installed" event and the card names the extension.
- Merge migrations 0032 + 0033 into a single 0032_operation_traceability revision
  carrying the full table shape and an index set that matches the ORM.

Tests: unit 5165 passed / integration 358 passed; ruff check + format clean.

src/langbot/pkg/api/http/controller/groups/provider/models.py

@@ -3,7 +3,7 @@ import quart
 from langbot.pkg.provider.modelmgr import errors as provider_errors
 from ....authz import Permission, has_permission
 from ....context import RequestContext
-from ....service import settings as settings_service
+from ......operation_trace import service as settings_service
 from ... import group
 from .query import resolve_include_secret
 

src/langbot/pkg/api/http/controller/groups/provider/providers.py

@@ -2,7 +2,7 @@ import quart
 
 from ....authz import Permission, has_permission
 from ....context import RequestContext
-from ....service import settings as settings_service
+from ......operation_trace import service as settings_service
 from ... import group
 from .query import resolve_include_secret