fix: do not split If-None-Match entity-tags on commas inside quotes

[official-burak]

parseTokenList treated every comma as a list separator. RFC 9110 opaque-tag allows commas inside the quoted entity-tag, so a validator sending W/"foo,bar" never matched that same ETag and fresh() returned stale.

Repro (2.0.0)

fresh(
  { 'if-none-match': 'W/"foo,bar"' },
  { etag: 'W/"foo,bar"' }
)
// => false  (expected true)

The list was parsed as W/"foo and bar", neither of which equals W/"foo,bar".

Change

Track double quotes while scanning so commas inside an opaque-tag stay in that token. Commas outside quotes still separate the list. Existing spacing and weak/strong matching tests are unchanged.

Tests

• exact match on W/"foo,bar"
• still splits W/"foo,bar", "baz"
• a fragment that the old splitter would have produced (W/"foo) does not match

[kilisamemarisaaa]

Verified at fbbde9c on Windows with Node 24.12.0: npm test passes all 27 tests and npm run lint is clean. I also exercised seven additional cases covering strong and weak validators, multiple comma-bearing tags, an empty/comma-only opaque tag, fragment non-matches, and commas outside quotes; all produced the expected freshness result. The quote-state scan matches RFC 9110 opaque-tag grammar, where DQUOTE is excluded from etagc, so commas inside a valid quoted tag remain data while list commas still split. I found no correctness issues in this change.