* chore: add .claude/worktrees to gitignore * feat(web): update threading constants for redesign Replace viewport-specific indent caps with a universal cap of 10, viewport-specific indent steps in pixels, and a line opacity gradient. * feat(web): add useThreadIndent hook replacing useVisualIndentCap Returns viewport-aware indent step (px) and chevron visibility. Desktop: 22px + chevron, tablet: 16px + chevron, mobile: 8px no chevron. * feat(web): redesign ThreadLine with chevron and opacity support Add CaretDown/CaretRight chevron indicators (hidden on mobile via showChevron prop). Add opacity prop for ancestor line fade effect. Line and chevron share hover color transition. * feat(web): add AncestorLines component for ancestor thread lines Renders one ThreadLine per ancestor depth with opacity fading from right (direct parent, full opacity) to left (distant ancestor, dim). Each line independently collapses its ancestor's sub-thread. * feat(web): rewrite ReplyBranch with unified line system Remove border-l nesting divs. Pass ancestor line data through recursion so each comment renders all ancestor lines to its left. Use pixel-based indent steps. Cap visual depth at 10. * feat(web): wire ReplyThread to new indent hook and ReplyBranch props Replace useVisualIndentCap with useThreadIndent. Pass indentStep and showChevron through to ReplyBranch. Remove old hook.