brrrn v0.1.3

Hub-only release. It is deployed to the Cloudflare Worker and needs no app or
engine update; existing installs keep working unchanged.

This removes the main source of Workers KV load. The pit board used to read
every stored machine-day for every member on each request, so a board view
generated KV reads that grew with a member's whole history rather than with
what anyone actually did. On an account near the KV daily read limit, that is
what pushed usage over the edge.

Changed

• The pit board is served from a per-member, per-machine summary kept in the
  Coordinator's Durable Object storage instead of scanning every stored
  machine-day on each request. A board read no longer grows with a member's
  history. Board requests now route through the Coordinator so they can read
  that storage. The board response is unchanged.
• Submit maintains that summary in step with the day records: cost per UTC day
  (for the today, week, and month windows and for streaks) and the current
  week's model breakdown, tracked per machine. Cost is set per machine and
  date, so a re-submit overwrites its own value instead of double-counting.
  The summary lives in strongly consistent storage, so a KV write limit can
  never leave it stale.

Added

• Submit rejects records dated after the current UTC day, matching the v2
  routes.

Notes

• Summaries build lazily. The first submit from each member after this deploy
  rebuilds theirs from existing day records; until then the board falls back to
  the old scan for that member. A machine the migration cannot see yet rebuilds
  from its own records on its next submit. No data migration or backfill is
  required.
• Audited end to end with headless Codex before merge.