feat(nostr adapter): 新增Nostr会话处理和线程模拟工具

新增两个文件实现Nostr适配器的基础工具能力：
1. session.py：实现聊天ID、线程键、代理路由的解析与目标标准化
2. thread_simulator.py：实现Nostr事件线程链构建、标签解析和事件缓存获取功能

backend/package/yuxi/channels/adapters/nostr/session.py

@@ -0,0 +1,31 @@
+from __future__ import annotations
+
+from yuxi.channels.models import ChannelMessage
+
+
+def resolve_thread_key(message: ChannelMessage) -> str:
+    identity = message.identity
+    chat_id = identity.channel_chat_id
+
+    if chat_id.startswith("dm:"):
+        pubkey = chat_id.removeprefix("dm:")
+        return f"nostr:dm:{pubkey}"
+    if chat_id.startswith("channel:"):
+        channel = chat_id.removeprefix("channel:")
+        return f"nostr:channel:{channel}"
+    return f"nostr:unknown:{chat_id}"
+
+
+def resolve_chat_id(message: ChannelMessage) -> str:
+    return message.identity.channel_chat_id
+
+
+def resolve_agent_route(message: ChannelMessage, default_agent_id: str = "default") -> str:
+    thread_key = resolve_thread_key(message)
+    return f"agent:{default_agent_id}:{thread_key}"
+
+
+def normalize_target(target: str) -> str:
+    if target.startswith("nostr:"):
+        return target
+    return f"nostr:{target}"

backend/package/yuxi/channels/adapters/nostr/thread_simulator.py

@@ -0,0 +1,69 @@
+from __future__ import annotations
+
+from typing import Any
+
+
+class NostrThreadSimulator:
+    def __init__(self, relay_pool: Any = None, max_depth: int = 10):
+        self._relay_pool = relay_pool
+        self._event_cache: dict[str, dict] = {}
+        self._reply_chains: dict[str, list[str]] = {}
+        self._max_depth = max_depth
+
+    async def build_thread_from_event(self, event: dict) -> list[dict]:
+        chain: list[dict] = []
+        current = event
+
+        for _ in range(self._max_depth):
+            chain.append(current)
+            parent_id = self._get_parent_event_id(current)
+            if not parent_id:
+                break
+            parent = await self._fetch_event(parent_id)
+            if not parent:
+                break
+            current = parent
+
+        return list(reversed(chain))
+
+    @staticmethod
+    def _get_parent_event_id(event: dict) -> str | None:
+        tags: list[list[str]] = event.get("tags", [])
+        for tag in tags:
+            if tag[0] == "e":
+                if len(tag) >= 4 and tag[3] == "reply":
+                    return tag[1]
+                if len(tag) >= 2:
+                    return tag[1]
+        return None
+
+    @staticmethod
+    def resolve_e_tags(event: dict) -> list[str]:
+        tags: list[list[str]] = event.get("tags", [])
+        return [tag[1] for tag in tags if tag[0] == "e" and len(tag) > 1]
+
+    @staticmethod
+    def resolve_p_tags(event: dict) -> list[str]:
+        tags: list[list[str]] = event.get("tags", [])
+        return [tag[1] for tag in tags if tag[0] == "p" and len(tag) > 1]
+
+    def _is_root_event(self, event: dict) -> bool:
+        tags: list[list[str]] = event.get("tags", [])
+        for tag in tags:
+            if tag[0] == "e" and len(tag) >= 4 and tag[3] == "root":
+                return False
+        return True
+
+    async def _fetch_event(self, event_id: str) -> dict | None:
+        if event_id in self._event_cache:
+            return self._event_cache[event_id]
+
+        if self._relay_pool:
+            try:
+                event = await self._relay_pool.query_event(event_id)
+                if event:
+                    self._event_cache[event_id] = event
+                    return event
+            except Exception:
+                pass
+        return None