Claude brand palette, mobile responsiveness, shared-space markers

Changed

• Re-skinned to Claude brand colors. Accent moved from violet #7c5cfc to Claude coral #d97757 on warm-ivory (light) / warm-dark (#1f1e1d) neutrals. All swaps live in app/globals.css design tokens; tailwind.config.ts and the few hardcoded violet rgba()s in app/page.tsx + components/AIPanel.tsx updated to match so the accent is consistent everywhere.

Added

• Mobile responsiveness (progressive disclosure). The TopBar no longer overflows on phones: the focus timer is desktop-only, and Integrations + theme toggle collapse into a new "More" overflow menu (cs-mobile-only). The Share button is icon-only on mobile, the bottom toolbar shrinks and is width-capped, and the canvas zoom rail is hidden on touch (pinch-to-zoom). New .cs-desktop-only / .cs-mobile-only helpers + a max-width:600px block in app/globals.css.
• Shared vs. private spaces. listSpaces() now annotates each space with a share state (private / shared / incoming) from its membership + pending invites. A new ShareBadge in the TopBar marks shared spaces in the picker and the active-space pill — accent-tinted when a space was shared with you.