improve: welcome readers with the new community invitation

[hannesrudolph]

What Problem This Solves

The community invitation needs a welcoming message and clear actions for connecting with OpenClaw on each social platform.

User Impact

Readers see “Pull up a chair.” with the approved AI-future copy, light/dark artwork of three lobsters and one empty chair, and Reddit/Discord/X icon buttons labeled Join / Join / Follow. The invitation follows the page theme in all 21 locales.

Why This Change Was Made

This implements the reviewed workshop design in the existing docs invitation. White platform marks align with the body text, the artwork fades into the actual theme surface, and buttons use native neutral control colors. Existing dismissal preferences, mobile navigation behavior, and rounded desktop Safari fallback remain in place.

Evidence

• 218 tests passed.
• All 20 Chromium/WebKit banner checks passed, covering light/dark, desktop/mobile, keyboard order, theme-specific artwork, icon alignment, touch targets, bounds, dismissal persistence and cross-tab synchronization.
• Russian and Persian previews fit at desktop and 320px mobile widths; RTL icon alignment was verified.
• All 21 locales retain the visible action words in their accessible names.
• Source autoreview completed. Its narrow-desktop warning assumed an obsolete 220px card; the later 300px override and rendered Russian/Ukrainian checks at 821px and 1024px disprove it. No accepted findings remain. Artwork was reviewed separately because the source-review helper rejects binary diffs.

Dark: before	Dark: after

Light: before	Light: after

Mobile and RTL screenshots