feat: add group message flow context mode

[Tsukumi233]

为群聊上下文感知新增 flow 模式，让现代长上下文模型可以按群聊消息流增量接收上下文，而不是每次只依赖滑动窗口。默认仍为 sliding_window，现有用户不启用新模式时行为保持不变。

Modifications / 改动点

• 新增 GroupMessageFlowRecord 和 GroupMessageFlowCursor 数据表，用于持久化群聊消息流以及每个 conversation 的消费游标。
• 在群聊上下文感知中新增 group_context_mode，支持 sliding_window 与 flow 两种模式；flow 模式会在 LLM 请求前注入 <group_messages_delta>，并排除当前触发消息，避免重复上下文。
• 为 flow delta 增加安全边界：group_flow_max_delta_messages 每次只注入最近 N 条消息，默认 200；group_flow_max_message_chars 每条消息只保留前 N 个字符，默认 1000；两者均可设为 0 关闭对应限制。
• 兼容 /reset 和 /new 等会话清理路径：清理后将 flow 游标推进到最新消息，使新会话不会带入旧 delta。
• 默认不记录 LLM 自己的回复；新增 group_flow_record_bot_messages 仅控制命令或插件产生的普通机器人消息。
• 增加消息组件 JSON-safe 序列化，覆盖 Reply 内嵌 Plain 等嵌套组件，并兼容同步/异步 to_dict()，避免 flow 落库时报 not JSON serializable。
• 增加 WebUI 配置项和中/英/俄 i18n，包括 flow/sliding_window 选项标签。
• This is NOT a breaking change. / 这不是一个破坏性变更。

Screenshots or Test Results / 运行截图或测试结果

验证步骤：

jq empty dashboard/src/i18n/locales/zh-CN/features/config-metadata.json dashboard/src/i18n/locales/en-US/features/config-metadata.json dashboard/src/i18n/locales/ru-RU/features/config-metadata.json
node - <<'NODE'
const fs = require('fs');
const files = [
  'dashboard/src/i18n/locales/zh-CN/features/config-metadata.json',
  'dashboard/src/i18n/locales/en-US/features/config-metadata.json',
  'dashboard/src/i18n/locales/ru-RU/features/config-metadata.json',
];
const keys = [
  'ext_group.ltm.provider_ltm_settings.group_context_mode.description',
  'ext_group.ltm.provider_ltm_settings.group_context_mode.hint',
  'ext_group.ltm.provider_ltm_settings.group_context_mode.labels',
  'ext_group.ltm.provider_ltm_settings.group_flow_max_records.description',
  'ext_group.ltm.provider_ltm_settings.group_flow_max_delta_messages.description',
  'ext_group.ltm.provider_ltm_settings.group_flow_max_message_chars.description',
  'ext_group.ltm.provider_ltm_settings.group_flow_record_bot_messages.description',
];
for (const file of files) {
  const data = JSON.parse(fs.readFileSync(file, 'utf8'));
  for (const key of keys) {
    let value = data;
    for (const part of key.split('.')) value = value && value[part];
    if (!value) throw new Error(`${file} missing ${key}`);
  }
}
console.log('i18n keys ok');
NODE
uv run ruff format --check astrbot/builtin_stars/astrbot/long_term_memory.py astrbot/core/config/default.py astrbot/core/db/__init__.py astrbot/core/db/sqlite.py tests/test_group_message_flow.py
uv run ruff check astrbot/builtin_stars/astrbot/long_term_memory.py astrbot/core/config/default.py astrbot/core/db/__init__.py astrbot/core/db/sqlite.py tests/test_group_message_flow.py
uv run pytest tests/test_group_message_flow.py
uv run pytest
cd dashboard && pnpm install --frozen-lockfile && pnpm typecheck

结果：

i18n keys ok
5 files already formatted
All checks passed!
tests/test_group_message_flow.py: 7 passed
uv run pytest: 1293 passed, 4 warnings
pnpm install --frozen-lockfile: Done
pnpm typecheck: passed

---

Checklist / 检查清单

• 😊 If there are new features added in the PR, I have discussed it with the authors through issues/emails, etc.
  / 如果 PR 中有新加入的功能，已经通过 Issue / 邮件等方式和作者讨论过。

• 👀 My changes have been well-tested, and "Verification Steps" and "Screenshots" have been provided above.
  / 我的更改经过了良好的测试，并已在上方提供了“验证步骤”和“运行截图”。

• 🤓 I have ensured that no new dependencies are introduced, OR if new dependencies are introduced, they have been added to the appropriate locations in requirements.txt and pyproject.toml.
  / 我确保没有引入新依赖库，或者引入了新依赖库的同时将其添加到 requirements.txt 和 pyproject.toml 文件相应位置。

• 😮 My changes do not introduce malicious code.
  / 我的更改没有引入恶意代码。

[sourcery-ai]

Hey - I've found 2 issues, and left some high level feedback:

• In LongTermMemory._json_safe you call isinstance(value, list | tuple), but list | tuple creates a types.UnionType which isinstance does not accept and will raise a TypeError; use a tuple of types instead (e.g., isinstance(value, (list, tuple))).

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- In `LongTermMemory._json_safe` you call `isinstance(value, list | tuple)`, but `list | tuple` creates a `types.UnionType` which `isinstance` does not accept and will raise a `TypeError`; use a tuple of types instead (e.g., `isinstance(value, (list, tuple))`).

## Individual Comments

### Comment 1
<location path="astrbot/builtin_stars/astrbot/long_term_memory.py" line_range="239" />
<code_context>
+            return await self._json_safe(value.toDict())
+        if isinstance(value, dict):
+            return {k: await self._json_safe(v) for k, v in value.items()}
+        if isinstance(value, list | tuple):
+            return [await self._json_safe(item) for item in value]
+        return value
</code_context>
<issue_to_address>
**issue (bug_risk):** Using `isinstance(value, list | tuple)` will raise at runtime; `isinstance` does not accept `|` unions here.

`isinstance` requires a type or a tuple of types as its second argument; `list | tuple` (PEP 604 union) will raise `TypeError` at runtime, so this branch will fail for lists/tuples. Use `isinstance(value, (list, tuple))`, or `collections.abc.Sequence` if you need broader sequence support.
</issue_to_address>

### Comment 2
<location path="astrbot/builtin_stars/astrbot/long_term_memory.py" line_range="224-225" />
<code_context>
+        return content
+
+    async def _component_to_json_safe_dict(self, comp) -> dict:
+        if hasattr(comp, "to_dict"):
+            data = await comp.to_dict()
+        elif hasattr(comp, "toDict"):
+            data = comp.toDict()
</code_context>
<issue_to_address>
**issue (bug_risk):** Blindly awaiting `comp.to_dict()` assumes it is async; if it is sync this will fail at runtime.

Both `_component_to_json_safe_dict` and `_json_safe` currently assume any `to_dict` is async. If `to_dict` is a regular sync method returning a dict (a common case), `await comp.to_dict()` will raise `TypeError: object dict can't be used in 'await' expression`. Consider checking whether `to_dict` is awaitable (e.g. via `inspect.iscoroutinefunction` / `inspect.isawaitable`) and only `await` it when appropriate, otherwise call it synchronously.
</issue_to_address>

---

Sourcery is free for open source - if you like our reviews please consider sharing them ✨

• X
• Mastodon
• LinkedIn
• Facebook

_{Help me be more useful! Please click 👍 or 👎 on each comment and I'll use the feedback to improve your reviews.}

[gemini-code-assist]

Code Review

This pull request introduces a new 'flow' mode for group chat context management, which persists group messages and uses conversation cursors to provide a more stable long-term memory compared to the traditional sliding window. The implementation includes new database models for message records and cursors, a dedicated GroupMessageFlowManager, and updates to the configuration and core lifecycle to support these features. I have no feedback to provide.