feat(FR-255): synchronize the file input in the LLM Playground.

[agatha197]

resolves #2861 (FR-255)

Adds file attachment synchronization support to the LLM chat interface, enabling consistent file handling across multiple chat instances. When files are attached in one chat window, they are now properly synchronized across all active chat sessions.

Changes:

• Introduces synchronizedAttachmentState atom for managing shared file attachments
• Adds file attachment handling in EndpointLLMChatCard
• Implements createDataTransferFiles utility function for consistent file processing
• Updates attachment state management in LLMChatCard

Checklist:

• Documentation
• Minium required manager version
• Specific setting for review:
  • Test file attachments in synchronized chat mode
  • Verify attachments persist across chat instances
• Minimum requirements to check during review:
  • File attachments sync correctly between chat windows
  • Attachments clear properly after submission
  • Supported file types (image/, text/) work as expected
• Test cases:
  1. Attach files in one chat window, verify sync in others
  2. Submit message with attachments, confirm proper clearing
  3. Test with various file types to ensure compatibility

Screenshots:
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[agatha197]

• feat(FR-255): synchronize the file input in the LLM Playground. #3032 👈 (View in Graphite)
• main

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Coverage report for ./react

St.❔	Category	Percentage	Covered / Total
🔴	Statements	4.95% (-0.01% 🔻)	398/8046
🔴	Branches	4.26% (-0.01% 🔻)	237/5566
🔴	Functions	2.97% (-0% 🔻)	78/2630
🔴	Lines	4.87% (-0.01% 🔻)	383/7872

Test suite run success

124 tests passing in 14 suites.

Report generated by 🧪jest coverage report action from f0b7278