v0.1.0-rc.1

Audit fixes + benchmark evidence

- quantile: promote_exact overflowed f64 on extreme spans (hi/lo=inf); now
  computed in log space, bucket count capped at MAX_BUCKETS (+ regression test)
- hub: rate-limiter retry_after_ms used subsecond millis instead of position
  in the minute; fixed
- server/bin: saturated UDP datagrams now account every dropped event
- query: table detection tolerates arbitrary whitespace/newlines in SQL
- loadgen: concurrency workers, latency percentiles, UDP mode, StdRng (Send)
- docs: BENCHMARKS.md filled with measured ladder (100k/s, 0 drops, ~32MB RSS,
  SQL timings, crash drill); README status/benchmarks/implementation notes;
  ROADMAP honestly ticked