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/parse_request.py

@@ -9,6 +9,13 @@ supply one interactively.
 Routing (`_next`):
   - prompt present -> (no _next; static next: plan)
   - prompt empty   -> ask_topic
+
+Fail-safe (R3): a crash here (e.g. malformed GRAPH_STATE) means the
+caller's prompt cannot be read at all, so proceeding silently is
+meaningless — the degraded route is `ask_topic`, which asks the user for
+the topic directly, plus a PIPELINE-FAULT entry so the loss is visible in
+the final report's Pipeline notes. Clobbering `pipeline_faults` is safe
+here: this is the start node, so the list can only hold its initial [].
 """
 import json
 import os
@@ -31,5 +38,17 @@ def main():
         print(json.dumps({"_next": "ask_topic"}))
 
 
-if __name__ == "__main__":
+try:
     main()
+except Exception as e:  # noqa: BLE001 — a crashed entry router must degrade, not die
+    print(
+        json.dumps(
+            {
+                "_next": "ask_topic",
+                "pipeline_faults": [
+                    f"PIPELINE-FAULT: request parsing crashed — {e}; asked the "
+                    "user for the research topic instead"
+                ],
+            }
+        )
+    )