sandbox phase 6 (UI): AR manifest page + lineage drawer

[William-Hill]

Parent: #116 · Spec: docs/superpowers/specs/2026-05-02-sis-pdp-ar-sandbox-design.md

Scope

• Route /sandbox/ar: shipping-manifest layout — filename (mono), bytes, rows, sha, generated-at, first-20-row CSV preview.
• Equal-weight "Download" and "Send to dashboard" buttons.
• Route /sandbox/lineage/[event_id]: 480px right drawer showing the full chain SIS row → PDP submission → AR file row → dashboard cell. Each segment is a link.
• Teal (#0F4C5C) stage tint on the AR page.

Acceptance

• AR manifest page renders for any AR file produced by phase 3
• CSV preview shows first 20 rows with sticky header
• Lineage drawer reachable from at least 3 representative dashboard surfaces (KPI, chart cell, table row) — partial fulfillment of feat: data lineage view — "where did this number come from" #107
• Lineage queries return < 1s on the sandbox dataset

Estimate: 2–3 days. Depends on phase 3. Closes part of #107.