Stellar Index v0.28.1

[v0.28.1] — 2026-08-08

Added

• Sub-second holders boards (inventory #4): ch-holders-rollup +
  30-min timer precompute every asset's top-500 holders + count into
  exchange-swapped rollup tables; /v1/assets/{id}/holders serves
  keyed reads with a probed fallback to the legacy scans. Part of the
  sub-second page goal (2026-08-08); scripts/ops/subsecond-audit.py
  is the goal's acceptance harness.

Fixed

• Saturation rejects no longer claim to be timeouts (inventory #5).
• /v1/readyz single-flight + 1s cache — unauthenticated spam can no
  longer exhaust the DB pool through the checkers (inventory #26).
• Migration 0137 disarms the comet replay double-count (inventory
  #19); REQUIRES projector-replay -source comet -from 51499000
  after deploy.