What it does

This commit fixes an issue where autocompletion would incorrectly trigger when typing a variable character '#' in the middle of words (e.g., "Hello#").

Changes:

• Removed '#' from trigger characters in the variable argument completion provider
• Improved boundary detection in the variable argument picker to prevent triggering when '#' appears within words
• Added better context validation to ensure completion only happens in appropriate cases
• Fixed the implementation to maintain correct functionality for legitimate variable references like "#file:"
• Refactored code to remove code duplication

The fix ensures that autocompletion is only triggered in intended contexts while preserving all existing functionality. Fixed #15028

How to test

In the chat Input view test different cases:

• starting with ~, @ or # should trigger the autocompletion
• continuing after a variable selection via #file with a : should trigger the argument selection
• typing Foo~, Foo@ or Foo# should not trigger the autocompletion
• typing Foo ~, Foo @ or Foo # should trigger the autocompletion

Follow-ups

Breaking changes

• This PR introduces breaking changes and requires careful review. If yes, the breaking changes section in the changelog has been updated.

Attribution

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines