chore(atomic): migrate to Tailwind V4

[fpbrault]

This PR updates tailwind to V4

https://coveord.atlassian.net/browse/KIT-3925
Also includes:
https://coveord.atlassian.net/browse/KIT-3926
https://coveord.atlassian.net/browse/KIT-3928

[github-actions]

Pull Request Report

PR Title

✅ Title follows the conventional commit spec.

Live demo links

• Storybook

• Playwright report

Bundle Size

File	Old (kb)	New (kb)	Change (%)
case-assist	243.7	243.7	0
commerce	355	355	0
search	415	415	0
insight	406.2	406.2	0
recommendation	255.9	255.9	0
ssr	408.8	408.8	0
ssr-commerce	372.7	372.7	0

[dmgauthier]

I am curious what motivated this quite major lib update in the middle of a framework transition...

I would feel more secure with screen video captures of some interfaces.

[fpbrault]

I am curious what motivated this quite major lib update in the middle of a framework transition...

I would feel more secure with screen video captures of some interfaces.

@dmgauthier It is actually part of our move to Lit, as we want to already have everything in place as we convert the components to Lit, instead of a second phase of changes later just for the upgrade to tailwind 4

[louis-bompart]

I am curious what motivated this quite major lib update in the middle of a framework transition...

I would feel more secure with screen video captures of some interfaces.

That's an excellent question, and the concern is well-placed.

The timing of the migration is a key decision factor. If we were in the middle of migration (i.e., components had already been migrated or "touched" CSS), we would have postponed the migration.
However, we are not: indeed, no components have been migrated yet, so doing the Tailwind 4 upgrade now is positive if we manage to do it with limited code changes.

You are right that if we had migrated components, we would have doubled the risk, as we would have had to check the two stacks, which would have been burdensome, and we would probably not have taken this risk. However, right now essentially:

• We migrate Stencil TW stack (cool).
• We ensure Lit is built straight on TW4, no migration to do afterward, and we rip some benefits right now (@fpbrault there were a couple, could you give some example to justify why the move is beneficial)

[fpbrault]

I am curious what motivated this quite major lib update in the middle of a framework transition...
I would feel more secure with screen video captures of some interfaces.

That's an excellent question, and the concern is well-placed.

The timing of the migration is a key decision factor. If we were in the middle of migration (i.e., components had already been migrated or "touched" CSS), we would have postponed the migration. However, we are not: indeed, no components have been migrated yet, so doing the Tailwind 4 upgrade now is positive if we manage to do it with limited code changes.

You are right that if we had migrated components, we would have doubled the risk, as we would have had to check the two stacks, which would have been burdensome, and we would probably not have taken this risk. However, right now essentially:

• We migrate Stencil TW stack (cool).
• We ensure Lit is built straight on TW4, no migration to do afterward, and we rip some benefits right now (@fpbrault there were a couple, could you give some example to justify why the move is beneficial)

Ability to replace most of our component-specific stylesheets with just tailwind classes, with the new selectors.
Smaller bundle size.
Faster build.
No need for extra postcss plugins in our build process.
You can also check this page for what is new in V4: https://tailwindcss.com/blog/tailwindcss-v4

[dmgauthier]

@fpbrault @louis-bompart
Thanks you for taking the time to address my concerns. That being said as of now, as long as we are making sure this is not breaking any layout. 🚢