A field whose tail is a non-empty prefix of a multi-character delimiter or
record delimiter must be quoted, otherwise the separator appended after it
re-tokenizes the boundary on parse and the value is silently corrupted:

  stringify([["a:", "b"]], { delimiter: "::" })            // a:::b
  parse("a:::b", { delimiter: "::" })                      // [["a", ":b"]]

The quoting predicate only checked `value.indexOf(separator) >= 0`, which
catches a field that contains the whole separator but misses this boundary
fusion. The same gap affected `record_delimiter`. Both now share an
`emits_separator` helper; single-character separators and non-fusing fields
are unaffected (no extra quoting). RFC 4180 §2.6, generalized to the library's
multi-character separators.

* fix: ship csv-parse stream cjs export

* test: cover csv-parse stream in cjs demo

#494)

* fix(csv-stringify): double regexp-metacharacter escape/quote literally

The escape and quote characters are configurable to any single character,
but when a quoted field contained the escape or quote char, the code doubled
occurrences via `new RegExp(escape, "g")` / `new RegExp(quote, "g")`. That
interpolates the user char into a pattern, so metacharacters misbehave:
`|` and `.` match everywhere and inject the doubled char at every position,
`*`/`+`/`?` throw "Nothing to repeat", and `^`/`$` anchor and silently no-op.

Replace the RegExp doubling with a literal `replaceAll` using a function
replacer, so neither the pattern nor a `$` in the replacement is interpreted.
This restores the round-trip invariant parse(stringify(x)) === x for any
configured escape/quote character.

* test(csv-stringify): dispatch 494 tests

(cherry picked from commit 662726b)

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Co-authored-by: David Worms <[email protected]>

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