fix(p1-backlog): 修復「待分析」死結與 Telegram 訊息截斷

問題 1：REQUEST_REVISION → 待分析
  根因：safe_candidates=[] → selected=None → recommended_action=None
        → decision_manager action="" → TG 卡顯示「待分析」（資訊流斷裂）
  修復 coordinator_agent.py：
    無安全候選時回退至 Solver 原始最優方案
    標記「[Reviewer 未核准，僅供參考] {action}」
    SRE 永遠能看到 AI 建議，資訊流絕不中斷

問題 2：debate_summary 在 (blast_radius... 中間截斷顯示 (bl
  根因：root_cause=reasoning[:150] — 150 字元對中文 debate_summary 過短
  修復 decision_manager.py：
    root_cause 截斷 150 → 300
    suggested_action 截斷 80 → 120

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/api/src/agents/coordinator_agent.py

@@ -133,9 +133,28 @@ class CoordinatorAgent(BaseAgent):
                 if c.action not in verdict.blocked_actions
             ]
             selected = safe_candidates[0] if safe_candidates else None
+
+            # 2026-04-17 ogt + Claude Sonnet 4.6: 無安全候選 → 回退 Solver 原始最優方案
+            # 根因：safe_candidates=[] → selected=None → recommended_action=None
+            #       → decision_manager action="" → TG 卡顯示「待分析」（資訊流斷裂）
+            # 修復：強制輸出 Solver 原始最優建議（標記 [Reviewer 未核准，僅供參考]）
+            #       資訊流絕不可斷，SRE 永遠需要看到 AI 的建議作為參考依據
+            _all_blocked = (selected is None and bool(plan.candidates))
+            if selected is None and plan.top_candidate:
+                selected = plan.top_candidate
+
             base_confidence = selected.confidence if selected else 0.0
+            if selected:
+                _recommended = (
+                    f"[Reviewer 未核准，僅供參考] {selected.action}"
+                    if _all_blocked
+                    else selected.action
+                )
+            else:
+                _recommended = "(無可用方案，請人工研判根因後執行)"
+
             return DecisionPackage(
-                recommended_action=selected.action if selected else None,
+                recommended_action=_recommended,
                 confidence=base_confidence,
                 requires_human_approval=True,
                 debate_summary=_build_summary(diagnosis, plan, verdict, critic),

apps/api/src/services/decision_manager.py

@@ -353,8 +353,8 @@ async def _push_decision_to_telegram(
                 approval_id=approval_id,
                 risk_level=risk_level,
                 resource_name=target[:50],
-                root_cause=reasoning[:150] if reasoning else description[:150],
-                suggested_action=action[:80] if action else "待分析",
+                root_cause=reasoning[:300] if reasoning else description[:300],
+                suggested_action=action[:120] if action else "待分析",
                 estimated_downtime="5-15 min",
                 primary_responsibility="INFRA",
                 confidence=confidence,