Link Guide categories to round id and scoring vocab

[PunchTheDev]

Summary

Guide The three categories cards now expose each category's round_id as a routed chip and connect the section to the canonical Rankings scoring vocabulary.

Changes

• QuickstartGuide.tsx L448–478: each category card gets a small mono round_001 / round_002 / round_003 chip (color-matched border, 122-char tooltip naming both the --round CLI flag and /problems/:roundId URL). Chip is a <Link> — click routes to that round's problem list.
• Added a How it's scored: trailing paragraph that reuses the exact Rankings header vocabulary (0.0 = best, 1.0 = worst (or unclaimed), round score, overall score) so the Guide and Rankings share a single source of truth instead of two parallel explanations. Ends with a routed see Rankings → link.
• QuickstartGuide.tsx L2: added Link import from react-router-dom.
• BACKLOG.md L109: The three categories flipped from ○ ○ ○ to ● ● ● with rationale + line range.

Verification

Puppeteer 1440×900 on /guide#categories:

• chipCount=3 with hrefs /problems/round_001 /problems/round_002 /problems/round_003, each tooltip = 122 chars
• Scoring paragraph present; see Rankings → link present and routes to /rankings
• Click round_001 chip → navigates to http://localhost:8080/problems/round_001
• 1 pre-existing console error (unchanged from prior steps)