Respect columns configuration when auto-sizing

[severo]

part of #228

I refactored the code a lot (and simplified the localStorage format), because it was too hard to understand. The code is not necessarily much shorter, but it's more explicit and easier to understand and maintain, I guess.

I changed some behaviors:

• the column-specific minWidth configuration is now respected
• an auto-resized column is not marked as fixed anymore (the small dot), as automatic sizing sets all the columns to their measured width by default
• the algorithm to shrink the column so that they try to fit in the component is now:
  • don't shrink the fixed columns
  • try to shrink the largest columns, then the second largest ones, etc.
  • a column cannot be shrunk below 33% of its measured width (which is capped by the CSS max-width: 40rem)
  • a column cannot be shrunk below 150px (to avoid having '...' instead of the header title)

Feel free to try the new behavior. I think it's more usable now.

Screencast.From.2025-10-02.23-03-37.mp4

[platypii]

So many providers 😆 but code looks cleaner, and I like the behavior better 👍