[Projects] Update Learning Projects teaser on /projects index

[andrewy1n]

Problem

ProjectsSection.tsx still uses placeholder copy for the Learning Projects card (“More details coming soon”), which undersells the program on /projects and Home.

Scope

• Replace the Learning Projects description string with one concise sentence covering Pupper, manipulation arms, teleop/VLA work, and the mobile platform (MiniAloha) without overflowing the card.
• Confirm where ProjectsSection is reused (e.g. Home) so layout still works.

Acceptance Criteria

• Teaser is accurate and non-placeholder.
• npm run lint passes.
• Playwright / visual tests updated if they assert the old string.

Files

• src/pages/Projects/ProjectsSection.tsx
• e2e/ (if copy is asserted)