[brightfootlimited-collab]

Summary

Closes #499

Adds comprehensive unit tests for lib/csv-parser.ts, covering all three exported functions across three input categories.

What was tested

Valid rows

• Multi-row parsing with auto-detected and aliased headers (address, total_amount, start_date, end_date, cliff_period)
• Optional columns: cliff_time, cliff_amount, cliff_duration
• CRLF line endings
• Whitespace trimming from cell values
• Blank lines interspersed in data (filtered out)
• Extra columns beyond the header (silently ignored)
• Header-only CSV with no data rows → zero rows, no errors
• Custom column mapping bypass

Invalid rows

• Missing required columns: recipient, amount, start_time/start_date, end_time/end_date
• Returns a descriptive error message and zero rows when required columns are absent

Malformed CSV input

• Unclosed quoted field → entire remainder of line consumed as one field, other fields default to ""
• Row shorter than expected → missing fields default to ""
• Row that is only commas → all fields are ""
• Blank lines after the header → zero rows, no errors
• Header with completely unrecognised column names → treated as data rows, no crash
• Quoted field containing literal \n text → parsed without crashing

parseDuration

• Plain integer seconds, all unit suffixes (s, m, h, d, w)
• Case-insensitive + surrounding whitespace tolerance
• Returns null for empty, non-numeric, float, negative, and unknown-suffix inputs

resolveCliffTime

• Absolute cliff_time, relative cliff_duration (duration suffixes + plain seconds)
• Priority: cliff_time wins over cliff_duration when both present
• Returns null when startTime is null (duration path)
• Returns null for unparseable cliff_time / cliff_duration
• End-to-end round-trips: CSV parsed by parseCsvBatch then cliff resolved by resolveCliffTime

Testing

Tests use Vitest + jsdom (existing project setup). No new dependencies added.