The CSV reader set has_headers(true) with no trimming and no header
check, so three real-world inputs failed silently or opaquely:
- A file with no header row had its first data row consumed as the
header and silently dropped.
- A leading UTF-8 BOM (Excel exports it) became part of the first
header name, breaking the `timestamp` column mapping.
- Leading/trailing whitespace around values broke serde parsing.
Add a BomStripReader<R> Read adapter that discards a leading EF BB BF,
set csv::Trim::All on the builder, and validate after opening that the
header names every required OHLCV column — a missing column now yields
a clear Error::Malformed instead of a silent misread. open/from_reader
route through a shared build() helper; from_reader and from_csv_reader
now return Result because header validation can fail.
kingchenc
6b468824ce