feat(dispatch): B2 LLM 動態 MCP 派發安全閘 + telegram_gateway LLM 按鈕流程

ADR-082 §B2：dispatch_llm_action() 風險閘控 + allowlist + 模板渲染
23 tests pass

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/api/src/services/callback_dispatcher.py

@@ -404,3 +404,165 @@ def _format_reply(
             text += "...\n<i>(已截斷)</i>"
         return f"{header}\n<pre>{text}</pre>"
     return f"{header}\n{mcp_result}"
+
+
+# =============================================================================
+# B2: LLM Dynamic Action Dispatcher
+# 2026-04-27 Claude Sonnet 4.6: B2 — dispatch_llm_action()
+# 支援 RecommendedAction 結構化動作的風險閘控 + allowlist 驗證 + 模板渲染
+# ADR-082 §B2：LLM 動態 MCP 規格派發安全閘
+# =============================================================================
+
+import re as _re
+
+
+def _render_llm_params(params: dict[str, str], context: dict) -> dict[str, str]:
+    """
+    渲染 RecommendedAction.params 模板。
+
+    支援兩個命名空間：
+    - {labels.xxx}   → context["labels"]["xxx"]
+    - {context.xxx}  → context["xxx"]（如 context.incident_id）
+    - {incident_id}  → context["incident_id"]（舊式相容）
+
+    渲染失敗的 key → 保留原始字串，不 crash。
+    """
+    def _repl(m: _re.Match) -> str:
+        key = m.group(1)
+        parts = key.split(".", 1)
+        try:
+            if parts[0] == "labels" and len(parts) == 2:
+                val = (context.get("labels") or {}).get(parts[1])
+                return str(val) if val is not None else m.group(0)
+            if parts[0] == "context" and len(parts) == 2:
+                val = context.get(parts[1])
+                return str(val) if val is not None else m.group(0)
+            # 舊式：直接 top-level key（如 {incident_id}）
+            val = context.get(key)
+            return str(val) if val is not None else m.group(0)
+        except Exception:
+            return m.group(0)
+
+    rendered: dict[str, str] = {}
+    for k, v in params.items():
+        if isinstance(v, str) and "{" in v:
+            try:
+                rendered[k] = _re.sub(r"\{([a-zA-Z0-9_.]+)\}", _repl, v)
+            except Exception:
+                rendered[k] = v
+        else:
+            rendered[k] = v
+    return rendered
+
+
+def _load_llm_tool_registry() -> dict[str, dict]:
+    """
+    Lazy import _load_mcp_tool_registry from solver_agent，避免 circular import。
+    失敗時返回 {} 並 log warning（不 crash）。
+    """
+    try:
+        from src.agents.solver_agent import _load_mcp_tool_registry  # noqa: PLC0415
+        return _load_mcp_tool_registry()
+    except Exception as exc:
+        logger.warning("llm_dispatch_registry_load_failed", error=str(exc))
+        return {}
+
+
+def dispatch_llm_action(
+    action: Any,
+    context: dict,
+) -> dict:
+    """
+    B2: LLM 動態 MCP 規格派發閘控器
+
+    安全層次（依序執行）：
+    1. Risk Gating  — critical 直接拒絕；high 需要 confirmed=True
+    2. Allowlist    — mcp_tool 必須在 registry 中
+    3. Params 渲染  — 支援 {labels.xxx} / {context.xxx} / {incident_id}
+    4. Nonce 生成   — medium/high 允許執行時附帶 nonce
+
+    Args:
+        action:  RecommendedAction dataclass（來自 solver_agent B1 輸出）
+        context: 執行上下文 dict（含 labels / incident_id / confirmed 等）
+
+    Returns:
+        dict — ok=True 為允許執行，ok=False 附 reason 拒絕原因
+    """
+    import time as _time  # noqa: PLC0415
+
+    risk: str = getattr(action, "risk", "medium")
+    mcp_tool: str = getattr(action, "mcp_tool", "")
+    mcp_provider: str = getattr(action, "mcp_provider", "")
+    name: str = getattr(action, "name", "")
+    params: dict = dict(getattr(action, "params", {}) or {})
+
+    # ── 1. Risk Gating ────────────────────────────────────────────────────────
+
+    if risk == "critical":
+        logger.warning(
+            "llm_dispatch_critical_rejected",
+            mcp_tool=mcp_tool,
+            name=name,
+            incident_id=context.get("incident_id"),
+        )
+        return {"ok": False, "reason": "critical_action_rejected"}
+
+    if risk == "high":
+        if not context.get("confirmed"):
+            nonce = (
+                f"{mcp_tool}:{name}:{context.get('incident_id', '?')}:{int(_time.time())}"
+            )
+            logger.info(
+                "llm_dispatch_high_risk_pending",
+                mcp_tool=mcp_tool,
+                name=name,
+                incident_id=context.get("incident_id"),
+            )
+            return {
+                "ok": False,
+                "reason": "high_risk_requires_confirmation",
+                "nonce": nonce,
+            }
+
+    # ── 2. Allowlist 驗證 ─────────────────────────────────────────────────────
+
+    registry = _load_llm_tool_registry()
+    if mcp_tool not in registry:
+        logger.warning(
+            "llm_dispatch_tool_not_in_registry",
+            mcp_tool=mcp_tool,
+            registry_keys=list(registry.keys()),
+        )
+        return {"ok": False, "reason": "tool_not_in_registry"}
+
+    # ── 3. Params 模板渲染 ────────────────────────────────────────────────────
+
+    rendered_params = _render_llm_params(params, context)
+
+    # ── 4. Nonce 生成（medium/high 允許時） ───────────────────────────────────
+
+    nonce: str | None = None
+    if risk in ("medium", "high"):
+        nonce = (
+            f"{mcp_tool}:{name}:{context.get('incident_id', '?')}:{int(_time.time())}"
+        )
+
+    logger.info(
+        "llm_dispatch_allowed",
+        mcp_tool=mcp_tool,
+        mcp_provider=mcp_provider,
+        name=name,
+        risk=risk,
+        incident_id=context.get("incident_id"),
+        has_nonce=nonce is not None,
+    )
+
+    return {
+        "ok": True,
+        "mcp_provider": mcp_provider,
+        "mcp_tool": mcp_tool,
+        "params": rendered_params,
+        "risk": risk,
+        "nonce": nonce,
+        "button_source": "llm",
+    }