Close [AI-259](https://linear.app/affine-design/issue/AI-259)
Close [AI-243](https://linear.app/affine-design/issue/AI-243)
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **New Features**
* Introduced a unified AI chat content component to manage and display
chat interactions.
* Added new chat block message components for improved chat message
rendering.
* **Refactor**
* Simplified and unified session management across all AI chat
components, now passing full session objects instead of session IDs.
* Updated component and property names for clarity and consistency
(e.g., chat message and block message components).
* Consolidated chat history and actions retrieval for a more streamlined
chat experience.
* Removed redundant session ID getters and replaced them with direct
session object usage.
* Streamlined chat panel and composer components by removing internal
message and context state management.
* **Bug Fixes**
* Improved handling of chat session state and loading, reducing
redundant state properties.
* Enhanced event handling to prevent errors when chat parameters are
missing.
* **Tests**
* Removed outdated chat clearing test cases to align with new chat state
management.
* **Chores**
* Updated import paths and reorganized module exports for better
maintainability.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
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