fix(Table): preserve widths when header is hidden

[fallintoplace]

Why?

When showHeader={false}, the table used to remove <colgroup> together with <thead>. That dropped configured column widths even though column layout should not depend on whether the header is visible.

What changed

• Keep the table column group mounted when showHeader={false}.
• Preserve configured column widths without rendering the header.
• Keep the existing width and resize resolution logic unchanged.
• Added unit coverage for visible and hidden headers.
• Updated the NoHeader visual snapshots.

Regression coverage

The NoHeader visual test uses 220px, 200px, and 180px columns inside a 400px container with scrolling enabled, so it checks the actual overflow layout too.

Checks

• corepack yarn test --run
• corepack yarn typecheck
• corepack yarn lint:code
• corepack yarn lint:css
• corepack yarn build
• Linux Playwright visual test for NoHeader

[changeset-bot]

🦋 Changeset detected

Latest commit: 1169e8f

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@clickhouse/click-ui	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[Copilot]

Pull request overview

Fixes Table layout so configured column widths remain applied even when showHeader={false}, by keeping the <colgroup> mounted independently of <thead>.

Changes:

• Extracted <colgroup> rendering into a dedicated Colgroup component and render it unconditionally within the table.
• Simplified Thead to only render header rows/cells (no longer responsible for <colgroup>).
• Added unit tests verifying colgroup/col widths are preserved with both visible and hidden headers, plus a changeset entry.

Reviewed changes

Copilot reviewed 3 out of 5 changed files in this pull request and generated no comments.

File	Description
src/components/Table/Table.tsx	Keeps <colgroup> mounted regardless of header visibility to preserve column width behavior.
src/components/Table/Table.test.tsx	Adds coverage ensuring configured widths are present when header is shown/hidden.
.changeset/fix-table-widths-without-header.md	Declares a patch release note for the width preservation fix.

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[XOP]

@fallintoplace please rebase from main, this will allow to run VRT, thank you!

[XOP]

✅ Ready to be merged, but will be included in the next release after upcoming one