`parse_number_format` read the precision as `fmt[i+1..].parse::<u8>()` over
everything after the last `.`, so `,.2f` — the printf spelling the repo-map's
own `.improv` example carries — failed to parse and fell through to zero
decimals, silently, in the TUI, the browser projection and CSV export.
The precision is now the leading digit run after the last `.`, with any
conversion letter ignored. The spellings that are legal are stated once, in
`context/code/core.md`, along with why the trailing `f` is accepted rather than
refused (the grammar takes the format line as an opaque `rest_of_line`, so
refusing it rejects documents this repo already writes) and why the reading is
printf's rather than Excel's (`.00` is the spelling the two disagree on).
`export_csv_quotes_commas_per_rfc4180` asserted the value `starts_with("1,200")`
against a `,.2f` fixture, so it could not tell two decimals from none. It is now
an exact equality, and reverting the fix fails it.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FC2jVn8Au7E9JPkw6bwXXH
Edward Langley
3775d4ea1a