Fix chatops-lark bot to handle rich text messages

[Copilot]

The bot only parsed plain text messages (message_type: "text"), silently ignoring rich text messages (message_type: "post") sent with code blocks or formatting.

Changes

• Added rich text message parsing: Implemented structures and logic to extract text from Lark's post message format, which contains language-specific content arrays with tagged elements
• Unified message extraction: Created extractTextFromMessage() that handles both message types, preserving @mentions as @_user_N placeholders for regex matching
• Updated command parsers: Both parseGroupCommand() and parsePrivateCommand() now use the new extraction function

Example

Rich text messages now parse correctly:

// Post message structure from Lark
{
  "zh_cn": {
    "content": [
      [
        {"tag": "at", "user_id": "ou_xxx"},
        {"tag": "text", "text": " /ask what is TiDB?"}
      ]
    ]
  }
}

// Extracts to: "@_user_1 /ask what is TiDB?"
// Bot now responds instead of silently ignoring

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[chatops-lark] it did not response for rich format message.</issue_title>
<issue_description>I sent to the bot with the message but it has no feedback.

</issue_description>

<agent_instructions>please address the issue of chatops-lark project.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes [chatops-lark] it did not response for rich format message. #279

---

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[ti-chi-bot]

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please ask for approval from wuhuizuo. For more information see the Code Review Process.
Please ensure that each of them provides their approval before proceeding.

The full list of commands accepted by this bot can be found here.

Details

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
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