docs: add Mona Sans webfonts

[mnkiefer]

• Adds Mona Sans webfont files and license
• Corrected video thumbnail references
• Make logo text center vertically with logo image
• Fixed page flickers

[Copilot]

Pull request overview

Adds Mona Sans webfonts to the docs site and updates related docs UI/media references to improve visual polish and reduce layout flicker.

Changes:

• Add Mona Sans webfonts (Regular/Bold) and wire them into the docs theme font stack (with preloads).
• Fix video thumbnail/poster references to point at existing assets under docs/public/videos/.
• Adjust header/logo CSS for better vertical alignment and reduce layout shift/flicker (e.g., scrollbar gutter stabilization intent).

Reviewed changes

Copilot reviewed 7 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
docs/src/styles/custom.css	Registers Mona Sans via @font-face, updates Starlight font variable, and tweaks scrolling/header styles.
docs/src/content/docs/setup/quick-start.mdx	Updates video thumbnail reference.
docs/src/content/docs/setup/quick-start.md	Updates HTML video poster reference.
docs/src/content/docs/setup/creating-workflows.mdx	Updates video thumbnail reference.
docs/src/components/CustomLogo.astro	Tweaks logo image CSS to prevent flex shrink/layout issues.
docs/src/components/CustomHead.astro	Preloads Mona Sans font assets.
docs/public/fonts/README.md	Documents bundled font files and license expectations.
docs/public/fonts/MonaSans-Regular.woff2	Adds Regular font asset.
docs/public/fonts/MonaSans-Bold.woff2	Adds Bold font asset.

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[Copilot]

This README states that MonaSans-LICENSE.txt is bundled/required for redistribution, but that file is not present in docs/public/fonts/ in this PR. Please add the license file (or adjust the README if the license is being tracked elsewhere) so the font redistribution terms are actually satisfied.

Suggested change

	License text (required for redistribution under OFL-1.1):
	- `MonaSans-LICENSE.txt`
	The docs CSS registers these via `@font-face` and uses `"Mona Sans"` as the first choice in `--sl-font`.
	License text (required for redistribution under OFL-1.1) is provided in the upstream Mona Sans distribution as `MonaSans-LICENSE.txt`. If you redistribute these font files, ensure that the Mona Sans license text is included alongside them.
	The docs CSS registers these via `@font-face` and uses `"Mona Sans"` as the first choice in `--sl-font`.