feat: implement step two of dataset creation with comprehensive UI components and hooks

[CodingOnStar]

Summary

feat: implement step two of dataset creation with comprehensive UI components and hooks

• Added new components for general chunking options, parent-child options, preview panel, and step two footer.
• Introduced hooks for document creation, indexing configuration, indexing estimation, preview state, and segmentation state.
• Created types for step two props and integrated them into the components.
• Implemented escape and unescape utility functions for handling special characters.
• Established a structured approach for managing dataset creation workflow, enhancing user experience and functionality.

Checklist

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran make lint and make type-check (backend) and cd web && npx lint-staged (frontend) to appease the lint gods

[gemini-code-assist]

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[Copilot]

Pull request overview

This PR refactors the step-two component of the dataset creation workflow by extracting logic into custom hooks and smaller components, improving maintainability and testability.

Key Changes:

• Extracted state management into 5 custom hooks (useSegmentationState, usePreviewState, useIndexingConfig, useIndexingEstimate, useDocumentCreation)
• Split monolithic component into 5 focused sub-components (GeneralChunkingOptions, ParentChildOptions, IndexingModeSection, PreviewPanel, StepTwoFooter)
• Added comprehensive test coverage with 2185 lines of tests
• Created escape/unescape utility functions for handling special characters

Reviewed changes

Copilot reviewed 15 out of 19 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
index.tsx	Refactored main component to use extracted hooks and sub-components
types.ts	Defined StepTwoProps interface
hooks/*	Implemented 5 custom hooks for state management and business logic
components/*	Created 5 focused sub-components for UI sections
escape.ts/unescape.ts	Utility functions for character escaping
index.spec.tsx	Comprehensive test suite covering hooks and components

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[WTW0313]

LGTM