docs: document isolated session impact on session_id and unified_msg_origin

[lingyun14beta]

Enabling Isolate Conversation (platform_settings.unique_session) rewrites the
session_id of group messages to a platform-specific composite ID, so
unified_msg_origin changes with it. Plugins that store or query data per group
by either value address a different session once the setting is toggled, and the
current docs never mention this.

Continues #7947, which was closed by the stale-PR cleanup, rebased on current
master.

Modifications / 改动点

• Warn about the rewrite in the message event guide, with the concrete before and
  after example and the event.get_group_id() recommendation (zh/en)
• Correct the AstrBotMessage.session_id comment: it holds the raw adapter value;
  only the event's session_id copy is rewritten
• State the mechanism in the platform_settings.unique_session reference page,
  which previously described only the conversational consequence (zh/en)
• Note the consequence where a stored unified_msg_origin is used as a
  conversation or history key (send-message, ai; zh/en)
• Mention that the composite separator is platform-specific (Lark uses %, not _)

9 files changed, 30 insertions(+), 3 deletions(-)

• 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

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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 checked the affected WebUI instructions and screenshots in docs/zh and docs/en against the changed navigation, page structure, and labels, and updated them in this PR (or explained why no documentation update is needed). For renamed, moved, or merged entry points, I included an old entry → new entry mapping in the documentation and changelog.
  / 我已对照变化后的 WebUI 入口、页面结构和术语，核对并在本 PR 中更新 docs/zh 和 docs/en 的相关操作说明与截图（或说明无需更新文档的原因）。入口改名、移动或合并时，已在文档和 changelog 中补充 旧入口 → 新入口 对照。

• 🤓 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。

Summary by Sourcery

Document the identifier changes and plugin considerations introduced by enabling isolated conversations.

Enhancements:

• Document how Isolate Conversation rewrites group-message session identifiers and unified message origins on supported platforms.
• Clarify the distinction between raw message session IDs and rewritten event session IDs, and recommend using event.get_group_id() for group-based storage and lookups.
• Document platform-specific identifier formats and warn about stability and targeting implications when storing unified_msg_origin.

Documentation:

• Update English and Chinese configuration, message-event, plugin, AI, and send-message documentation with isolated-session identifier behavior and usage guidance.

[sourcery-ai]

Hey - I've found 3 issues

Prompt for AI Agents

Please address the comments from this code review:

## Individual Comments

### Comment 1
<location path="docs/en/dev/astrbot-config.md" line_range="166" />
<code_context>

 Whether to enable **Isolate Conversation**. Defaults to `false`. On supported platforms, each group member has a separate conversation context when enabled. Unsupported platforms retain their existing context. Access to `/new` and `/reset` is controlled by [command permissions](../use/command.md), which follow conversation isolation by default.

+The setting also rewrites the session identifier of group messages: `session_id` becomes a platform-specific composite ID (on QQ, `sender ID_group ID`), and `unified_msg_origin` changes along with it. Plugins that store or query data per group should use `event.get_group_id()` to get the raw group ID; see [Handling Message Events](./star/guides/listen-message-event).
+
 #### `platform_settings.rate_limit`
</code_context>
<issue_to_address>
**DingTalk IDs lack group**

When a plugin relies on the documented composite ID format for a DingTalk group message, dingTalk’s unique-session builder sets `session_id` to `event.get_sender_id()` only, so the ID has no group component; a plugin expecting the documented sender-and-group format parses or uses the wrong per-group key.

Document that DingTalk’s builder returns only the sender ID, and avoid promising a composite ID format for every supported platform.

Also at `docs/zh/dev/astrbot-config.md:166`, `docs/en/dev/star/guides/listen-message-event.md:46-47`, `docs/zh/dev/star/guides/listen-message-event.md:46-47`.
</issue_to_address>

### Comment 2
<location path="docs/en/dev/star/guides/send-message.md" line_range="42" />
<code_context>
 )
 ```

+> [!WARNING]
+> The example above uses `unified_msg_origin` as the conversation history storage key. When **Isolate Conversation** (`platform_settings.unique_session`) is enabled, the `unified_msg_origin` of group messages changes, so the same group resolves to a different conversation depending on the setting. Use `event.get_group_id()` when you need to target a group; see [Handling Message Events](./listen-message-event).
+
</code_context>
<issue_to_address>
**Group ID breaks message sending**

When a plugin passes `event.get_group_id()` directly to `Context.send_message` as the send target, `Context.send_message` passes the raw group ID to `MessageSesion.from_str`, which raises `ValueError` because the ID is not a `unified_msg_origin` or `MessageSession`; the message is not sent.

Clarify that `event.get_group_id()` is for group identification, not a `Context.send_message` target; use a `unified_msg_origin` or `MessageSession` to send.

Also at `docs/zh/dev/star/guides/send-message.md:42-43`, `docs/en/dev/star/guides/send-message.md:43`.
</issue_to_address>

### Comment 3
<location path="docs/en/dev/astrbot-config.md" line_range="166" />
<code_context>

 Whether to enable **Isolate Conversation**. Defaults to `false`. On supported platforms, each group member has a separate conversation context when enabled. Unsupported platforms retain their existing context. Access to `/new` and `/reset` is controlled by [command permissions](../use/command.md), which follow conversation isolation by default.

+The setting also rewrites the session identifier of group messages: `session_id` becomes a platform-specific composite ID (on QQ, `sender ID_group ID`), and `unified_msg_origin` changes along with it. Plugins that store or query data per group should use `event.get_group_id()` to get the raw group ID; see [Handling Message Events](./star/guides/listen-message-event).
+
 #### `platform_settings.rate_limit`
</code_context>
<issue_to_address>
**Session IDs stay unchanged**

When isolate Conversation is enabled on a platform without a registered unique-session builder, `build_unique_session_id` returns `None`, so `WakingCheckStage.process` leaves `event.session_id` unchanged and `unified_msg_origin` does not change; plugin authors expecting a changed key are misled.

Qualify the notices to say that session IDs change only on platforms with a unique-session builder.

Also at `docs/zh/dev/astrbot-config.md:166`, `docs/en/dev/star/guides/listen-message-event.md:46-47`, `docs/zh/dev/star/guides/listen-message-event.md:46-47`, `docs/en/dev/star/guides/ai.md:377`, `docs/zh/dev/star/guides/ai.md:375`, `docs/en/dev/star/guides/send-message.md:43`, `docs/zh/dev/star/guides/send-message.md:43`, `docs/zh/dev/star/plugin.md:134-135`.
</issue_to_address>

Sourcery assessment

Approval pending. 3 findings to address first.

Blocking findings: docs/en/dev/astrbot-config.md:166, docs/en/dev/star/guides/send-message.md:42, docs/en/dev/astrbot-config.md:166

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[sourcery-ai]

Sourcery assessment

Approved.