fix(honcho): read the sessionStart pin defensively in the first-turn formatter

tests and callers can build the provider without initialize(); the
formatter now treats a missing pin as unpinned instead of raising.

plugins/memory/honcho/__init__.py

@@ -405,7 +405,8 @@ class HonchoMemoryProvider(DialecticMixin, MemoryProvider):
         """Render the prefetch context, keeping only the ``injection.sessionStart`` components when pinned.
         The summary passes usable_honcho_summary here, so a contaminated one never reaches _base_context_cache."""
         ctx = {**ctx, "summary": usable_honcho_summary(ctx.get("summary")) or ""}
-        allowed = self._session_start_components
+        # getattr: tests build the provider without initialize().
+        allowed = getattr(self, "_session_start_components", None)
         parts, suppressed = [], []
         for name, key, header in _CONTEXT_SECTIONS:
             value = ctx.get(key, "")