Polish responsive gallery layout and support guidance

[adilei]

Summary

• use explicit 1-column mobile, 2-column tablet, and 3-column desktop solution grids
• show 1 partial featured card on mobile, 2 on tablet, and 3 on desktop
• keep the contributor filter trigger fixed when selection counts change
• contain the workflow selector's intrinsic width on narrow screens
• clarify that the gallery and submitted solutions are community examples outside Microsoft Support
• direct underlying Power Platform and Copilot Studio product issues to standard Microsoft support channels

Validation

• verified catalog and featured-card counts at 390px, 768px, and 1440px
• verified the contributor trigger has identical position and width before and after one or three selections across 81 viewport widths from 1200px to 2000px
• audited all 90 routes at 320px and 390px (180 checks total)
• confirmed zero horizontal overflow, graph-node overlaps, escaped graph controls, missing edge direction markers, or client exceptions
• visually reviewed the three-column desktop grid and representative mobile pages
• ran npm run astro -- check
• ran npm run build