[Chore/Refactor] Tighten MessageAgentThought type annotations

[laipz8200]

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Description

The MessageAgentThought SQLAlchemy model still relies on implicit column typing and lacks Mapped[...] annotations for several text and numeric fields. This gap generates mypy warnings under the SQLAlchemy plugin and leaves the message agent models inconsistent.

Motivation

Aligning this model with the rest of the typed ORM entities will unblock stricter static analysis for agent thought records and keep the message domain types consistent as we raise API type coverage.

[dosubot]

Hi, @laipz8200. I'm Dosu, and I'm helping the Dify team manage their backlog and am marking this issue as stale.

Issue Summary:

• You proposed enhancing type annotations in the MessageAgentThought SQLAlchemy model.
• The goal is to add explicit Mapped[...] types to text and numeric fields.
• This aims to remove mypy warnings from the SQLAlchemy plugin and improve type coverage.
• The change supports stricter static analysis and consistency with other ORM entities.
• There has been no further activity or comments on this issue.

Next Steps:

• Please let me know if this issue is still relevant to the latest version of Dify by commenting here.
• Otherwise, I will automatically close this issue in 15 days.

Thank you for your understanding and contribution!