feat(csv): add parseLine() convenience for single-line CSV records (refs #3765)

[MukundaKatta]

Summary

Refs #3765. Adds parseLine(line: string, options?: ParseLineOptions): string[] — a small synchronous convenience for single-record CSV input. Defaults to comma separator, no trim, strict quotes. Strips leading BOM and a single trailing CR/LF/CRLF.

API

parseLine("a,b,c")                       // ["a", "b", "c"]
parseLine("a\tb", { separator: "\t" })   // ["a", "b"]
parseLine('"a,b","c"')                   // ["a,b", "c"]

Documents the trade-off vs full parse() — parseLine doesn't continue multi-line quoted fields, doesn't validate field count across records, and doesn't honor comment lines. For those use parse.

Files changed

• csv/parse.ts — new ParseLineOptions interface and parseLine() function. Reuses internal Parser class. No breaking changes to existing parse() signature.
• csv/parse_test.ts — 12 new sub-steps covering basic parsing, quoting, escaped quotes, custom separator (TSV), trimLeadingSpace, lazyQuotes, trailing newline strip, BOM strip, error case, and return-type assertion.

Test plan

• deno fmt, deno lint, deno check, deno test all clean
• 11 passed, 0 failed (205 steps)
• Doc tests pass

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.61%. Comparing base (e356559) to head (960a7da).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7114   +/-   ##
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  Coverage   94.61%   94.61%           
=======================================
  Files         633      633           
  Lines       51777    51790   +13     
  Branches     9324     9330    +6     
=======================================
+ Hits        48987    49000   +13     
  Misses       2216     2216           
  Partials      574      574           

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