fix(runtime): suppress tool execution when provider safety-terminates with tool_calls (#3035)

* fix(runtime): suppress tool execution when provider safety-terminates with tool_calls

When a provider stops generation for safety reasons (OpenAI/Moonshot
finish_reason=content_filter, Anthropic stop_reason=refusal, Gemini
finish_reason=SAFETY/BLOCKLIST/PROHIBITED_CONTENT/SPII/RECITATION/
IMAGE_SAFETY/...), the response may still carry truncated tool_calls.
LangChain's tool router treats any non-empty tool_calls as executable,
so partial arguments (e.g. write_file with a half-finished markdown)
get dispatched and the agent loops on retry.

Add SafetyFinishReasonMiddleware at after_model: detect safety
termination via a pluggable detector registry, clear both structured
tool_calls and raw additional_kwargs.tool_calls / function_call,
preserve response_metadata.finish_reason for downstream observers,
stamp additional_kwargs.safety_termination for traces, append a
user-facing explanation to message content (list-aware for thinking
blocks), and emit a safety_termination custom stream event so SSE
consumers can reconcile any "tool starting..." UI.

Default detectors cover OpenAI-compatible content_filter, Anthropic
refusal, and Gemini safety enums (text + image). Custom providers are
added via reflection (same pattern as guardrails). Wired into both
lead-agent and subagent runtimes.

Closes #3028

* fix(runtime): persist safety_termination as a middleware audit event

Address review on #3035: the SSE custom event is great for live
consumers but invisible to post-run audit. RunEventStore should carry
its own row so operators can answer "which runs were safety-suppressed
today?" from a single SQL query without joining the message body.

Worker now exposes the run-scoped RunJournal via
runtime.context["__run_journal"] (sentinel key, internal channel).
SafetyFinishReasonMiddleware calls the previously-unused
RunJournal.record_middleware, which emits

  event_type = "middleware:safety_termination"
  category   = "middleware"
  content    = {name, hook, action, changes={
                  detector, reason_field, reason_value,
                  suppressed_tool_call_count,
                  suppressed_tool_call_names,
                  suppressed_tool_call_ids,
                  message_id, extras}}

Tool *arguments* are deliberately excluded — those are the very content
the provider filtered and persisting them would defeat the purpose of
the safety filter (per review note in #3035).

Graceful skips when journal is absent (subagent runtime, unit tests,
no-event-store local dev). Journal exceptions never propagate into the
agent loop.

Refs #3028

* fix(runtime): satisfy ruff format + address Copilot review

- ruff format on safety_finish_reason_config.py and e2e demo (CI lint
  failed on ruff format --check; backend Makefile lint target runs
  ruff check AND ruff format --check).
- Docstring on SafetyFinishReasonConfig now says resolve_variable to
  match the actual loader used in from_config (the wording was
  resolve_class previously; behavior is unchanged — resolve_variable
  mirrors how guardrails.provider is loaded).
- Switch the AIMessage type check in SafetyFinishReasonMiddleware._apply
  from getattr(last, "type") == "ai" to isinstance(last, AIMessage),
  matching TokenUsageMiddleware / TodoMiddleware / ViewImageMiddleware
  / SummarizationMiddleware which are the dominant pattern.

Refs #3028

backend/packages/harness/deerflow/agents/lead_agent/agent.py

@@ -29,6 +29,7 @@ from deerflow.agents.memory.summarization_hook import memory_flush_hook
 from deerflow.agents.middlewares.clarification_middleware import ClarificationMiddleware
 from deerflow.agents.middlewares.loop_detection_middleware import LoopDetectionMiddleware
 from deerflow.agents.middlewares.memory_middleware import MemoryMiddleware
+from deerflow.agents.middlewares.safety_finish_reason_middleware import SafetyFinishReasonMiddleware
 from deerflow.agents.middlewares.subagent_limit_middleware import SubagentLimitMiddleware
 from deerflow.agents.middlewares.summarization_middleware import BeforeSummarizationHook, DeerFlowSummarizationMiddleware
 from deerflow.agents.middlewares.title_middleware import TitleMiddleware
@@ -338,6 +339,15 @@ def _build_middlewares(
     if custom_middlewares:
         middlewares.extend(custom_middlewares)
 
+    # SafetyFinishReasonMiddleware — suppress tool execution when the provider
+    # safety-terminated the response. Registered after custom middlewares so
+    # that LangChain's reverse-order after_model dispatch runs Safety first;
+    # cleared tool_calls then flow through Loop/Subagent accounting without
+    # firing extra alarms. See safety_finish_reason_middleware.py docstring.
+    safety_config = resolved_app_config.safety_finish_reason
+    if safety_config.enabled:
+        middlewares.append(SafetyFinishReasonMiddleware.from_config(safety_config))
+
     # ClarificationMiddleware should always be last
     middlewares.append(ClarificationMiddleware())
     return middlewares