Live: per-agent counts on each tile #2

Goal. Each agent tile on live.setkernel.com shows that agent's numbers for today (UTC): issues started, pull requests opened, reviews, Claude requests.

Work

• src/logic.js: keep per-agent counts in the state next to counts, reset at UTC midnight the same way; only the four known agents.
• src/worker.js: include them in view().
• public/app.js: one compact line on each tile, e.g. 2 PRs · 4 reviews · 130 Claude, built with textContent only.
• test/logic.test.mjs: per-agent counting, the day reset, and unknown agents ignored.

Constraints. Uses only events the page already receives; nothing new leaves the publisher. Keep the strict CSP in public/_headers.

Done when npm run validate passes and the PR includes a screenshot from a local preview with sample data.

Tracking: setkernel/hq#105