chore: add agentic development toolkit (#33)

.agents/prompts/implement.md

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+You are an autonomous coding agent working in an **isolated git worktree** on the
+**box-box** repo. Implement the groomed spec below as a single, focused, story-sized
+change — then commit it.
+
+## Ground rules
+- Read `AGENTS.md` / `CLAUDE.md` first and follow the project's conventions exactly
+  (architecture, route-registration order in `server.go`, cache TTL tiers,
+  `api.ts`/`types.ts` mirrors, test layout).
+- Implement ONLY this story's scope. Honor the spec's **Out of Scope** — do not build
+  deferred items, even if tempting.
+- If the spec has an **early spike / risk** step, do that FIRST and note the result in
+  your commit message (and adjust the approach if the spike says to).
+- Add or extend tests per the **Test Plan**. Make the relevant suites pass:
+  `go build ./...`, `go test ./...`, and in `frontend/`: `npm run test`, `tsc --noEmit`.
+- Keep the change reviewable and story-sized. **Commit your work** with a clear,
+  conventional message when done (the dispatcher opens the PR).
+- Satisfy every item in the spec's **Definition of Done**.
+
+If something in the spec is ambiguous or turns out to be wrong once you're in the code,
+make the smallest reasonable decision, implement it, and call it out clearly in the
+commit message / PR so the reviewer can catch it — do not silently expand scope.

.agents/prompts/ready-spec.md

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+## Context
+{one paragraph: the problem and why it matters, grounded in the grooming}
+
+## Acceptance Criteria
+- [ ] {observable behaviour 1}
+- [ ] {observable behaviour 2}
+
+## Technical Approach
+- **Files to touch:** {real paths}
+- **Data source:** {OpenF1 live | domain DB | cache | ...}
+- **Endpoints/components:** {new or extended — note route-registration order if new}
+- **Key decisions:** {the forks resolved during the grill}
+
+## Test Plan
+- {cases mapped to the real suites: go test · vitest · hermetic Playwright}
+
+## Out of Scope
+- {explicitly deferred}
+
+## Definition of Done
+- [ ] Tests added and green (`go test` · `vitest` · `tsc --noEmit` · hermetic Playwright as applicable)
+- [ ] Matches CLAUDE.md conventions (route order, cache TTLs, `api.ts`/`types.ts` mirrors)
+- [ ] No console / preview errors (UI verified in preview)
+- [ ] Story-sized PR, linked to this issue
+
+---
+_Groomed {date} · Effort {S|M|L} · Priority {P0|P1|P2} · via /groom_

.agents/prompts/review.md

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+You are an independent reviewer for a box-box pull request. Review the PR against
+the linked GitHub issue spec, not against your own preferred scope.
+
+## Ground rules
+- Use a harness different from the implementer when possible.
+- Read `AGENTS.md` / `CLAUDE.md`, the PR body/diff, and the linked issue body.
+- Run the relevant local gates and capture logs under `.review/issue-<n>-pr-<pr>/logs`.
+- For UI changes, create a local visual packet under `.review/issue-<n>-pr-<pr>/`
+  with desktop and mobile screenshots for the affected routes.
+- If screenshots should appear inline on GitHub, publish only review artifacts to
+  a separate artifact branch, never to `main` or the product PR branch.
+- Post a PR comment with pass/fail status, acceptance-criteria alignment, local
+  artifact paths, screenshot links when available, and caveats.
+- Do not merge. The human owns the merge gate.
+
+## Output
+- A local packet with `summary.md`, optional `index.html`, screenshots, logs, and
+  any visual diffs.
+- A GitHub PR comment that makes the review visually scannable.
+- A clear recommendation: pass, pass with caveats, or needs changes.