feat(TASK-023): deep-research hardening — fail-safe scripts, fault fallbacks, pipeline notes

R3 guards: parse_request (crash → ask_topic), bootstrap_research,
combine_findings (crash → fault-text findings; also lifts branch-local
PIPELINE-FAULT findings into pipeline_faults, deduped), reflexion_gate
(crash fails forward to synthesize), incorporate_feedback (crash still
loops with a generic feedback note), verify_sources (top-level guard +
pipeline_notes fold).

Fallbacks per the plan's naming pins: plan → plan_fault → end_fault
(fail-closed; gains state_updates plan_failure per the TASK-016 rule);
research_one_question → branch-local question_fault (map collects the
fault finding); vet_sources/critique → degrade-visibly markers that
continue to the stage each node's own next pointed to; synthesize →
synth_fault → end_fault. end_fault renders
'DEEP_RESEARCH FAILED — PIPELINE-FAULT: <fault text>'.

Accepted-path visibility: verify_sources folds pipeline_faults into
pipeline_notes ('' when fault-free), appended to end_accepted's output
and the approval question — happy-path output stays byte-identical.
initial_state seeds questions: [] so a dying plan inside the static
fan-out leaves the sibling knowledge_lookup lane mapping over zero
items while end_fault renders.

R5: 19 python3-guarded regression tests + GraphParser wiring test;
bundled warning baseline unchanged.

assets/agents/deep-research/scripts/reflexion_gate.py

@@ -15,6 +15,12 @@ Routing (`_next`):
 Reflexion is a best-effort quality booster, not a hard gate: once the
 budget is spent the workflow proceeds anyway, and the human approval
 step is the final backstop.
+
+Fail-safe (R3): a crash here fails FORWARD to `synthesize` — the same
+direction as the existing malformed-critique PASS default — with a
+PIPELINE-FAULT entry recorded (best-effort preserving existing faults),
+so a broken gate costs the run its automated critique routing, never the
+run itself.
 """
 import json
 import os
@@ -33,6 +39,14 @@ def load_state():
     return json.loads(os.environ.get("GRAPH_STATE", "{}"))
 
 
+def safe_faults():
+    try:
+        state = load_state()
+        return [f for f in (state.get("pipeline_faults") or []) if isinstance(f, str)]
+    except Exception:  # noqa: BLE001 — best-effort preservation only
+        return []
+
+
 def as_int(value, default=0):
     try:
         return int(value)
@@ -72,5 +86,12 @@ def main():
     print(json.dumps(output))
 
 
-if __name__ == "__main__":
+try:
     main()
+except Exception as e:  # noqa: BLE001 — a crashed gate fails forward, never dies
+    faults = safe_faults()
+    faults.append(
+        f"PIPELINE-FAULT: reflexion gate crashed — {e}; proceeded to synthesis "
+        "without automated critique routing"
+    )
+    print(json.dumps({"_next": "synthesize", "pipeline_faults": faults}))