feat(ui-color-picker): improve ColorPicker paste behavior

[ToMESSKa]

INSTUI-4834

ISSUE:

• pasted hex color values can't replace existing values without manual clearing, e.g. pasting FF0000, then select all FF0000 and paste AABBCC resulted in nothing

TEST PLAN:

• selection replacement

  • paste FF0000, then select all FF0000 and paste AABBCC, the input should become AABBCC and result in valid color
  • in FF0000, select 00 in the middle, paste FF, it input should become FFFF00 and result in valid color

• cursor position

  • paste 0000, put the cursor at at the start of 0000 and paste FF, the input should become FF0000 and result in valid color
  • paste FF00, put the cursor in the middle of FF00 and paste AB, the input should become FFAB00 and result in valid color
  • put the cursor at the end of 0000 and Paste FF, the input should become 0000FF

• '#' stripping

  • paste #FF0000, it should still become FF0000
  • paste FF0000, it should still become FF0000

• length limits

  • Paste a 7-char string like FF00001, it should be still blocked

• invalid content

  • paste ZZZZZZ, it should be still blocked

[github-actions]

PR Preview Action v1.8.1
Preview removed because the pull request was closed.
2026-04-28 12:09 UTC

[ToMESSKa]

new pasted value previously always got appended at the end of the current one (e.g. FF0000 selected then AABBCC pasted → F0000AABBCC) and it was evaluated as invalid

[joyenjoyer]

looks good, I would add a few unit tests though

[ToMESSKa]

looks good, I would add a few unit tests though

@joyenjoyer I added some tests