fix: improve prompt history navigation to not interfere with text editing

[daniel-lxs]

This PR fixes the issue where up/down arrows would load old prompts instead of moving the cursor when editing multi-line text.

Changes:

• Up arrow only triggers history navigation when cursor is at the beginning of text
• Added Alt+Up/Down for explicit history navigation at any cursor position
• Down arrow in history mode works intelligently at both beginning and end of text
• History navigation resets when user types to avoid accidental loads
• Extracted prompt history logic into dedicated usePromptHistory hook

The default behavior now allows normal text editing with arrow keys, while still providing convenient access to prompt history when needed.

Fixes #4669

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Important

Improves prompt history navigation in ChatTextArea.tsx by using a new usePromptHistory hook and refining arrow key behavior.

• Behavior:
  • Up arrow triggers history navigation only at text start; Alt+Up/Down for navigation at any position.
  • Down arrow in history mode works at both text start and end.
  • History navigation resets on typing to prevent accidental loads.
• Hooks:
  • Extracted prompt history logic into usePromptHistory hook in usePromptHistory.ts.
• Misc:
  • Removed cursor positioning logic from ChatTextArea.tsx to simplify code.

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