New Model Support

• Added claudeOpus45 model type with proper temperature/top_p limitations
• Enabled reasoning, prompt caching, vision, and tool use support for Claude Opus 4.5
• Configured appropriate inference parameters for the new model

Architecture & Code Quality

• Separated image/document arrays in SharedMediaDataSource to fix index conflicts
• Added textPreviews array for proper pasted text identification
• Implemented addImage, addDocument, addPastedText helper methods for cleaner code
• Changed to saveFromUIMessages for consistent tool_use/tool_result storage
• Removed deprecated saveConversationHistory function
• Changed MessageData.user from let to var for tool result marking flexibility
• Large text (>10KB) automatically converted to file attachment with settings toggle

Bug Fixes

• Fixed ESC key to prioritize closing modals over stopping chat generation
• Fixed QuickAccessView height calculation after attachment removal
• Fixed parameter order in onSelectDocument callback
• Fixed pasted text not being sent to API correctly
• Fixed "Invalid signature in thinking block" error by only including thinking blocks when valid API signature exists
• Preserved thinking/signature data during tool use cycles
• Improved save/load performance with index-based message matching
• Added thinking/signature params to updateMessageWithToolInfo for proper state preservation

Additional Changes

• Added PastedTextInfo struct for storing pasted text metadata
• Pasted text sent as text blocks to avoid Bedrock's 5-document limit
• Preserved pasted text data across app restart via conversation history
• Added settings toggle for large text file attachment behavior

What's Changed

• feat: Add pasted text support, Claude Opus 4.5, and MCP tool use improvements by @didhd in https://github.com/aws-samples/amazon-bedrock-client-for-mac/commit/1d83eb7

Full Changelog: https://github.com/aws-samples/amazon-bedrock-client-for-mac/compare/v1.4.0...v1.4.1