fix: do not reuse the opening * when closing a comment

[spokodev]

Problem

/*/ does not round-trip — it comes back as /**/:

const valueParser = require("postcss-value-parser");
valueParser("/*/").toString();              // "/**/"
valueParser("a /*/ b").toString();          // "a /**/ b"
valueParser("/*/ hack /**/").toString();    // "/*/ hack /**/"  → "/**/ hack /**/"

/*/ is an unclosed comment whose content is /, but it is parsed as a closed, empty comment ({ type: "comment", value: "" }), and stringifying that yields /**/. This breaks the lossless round-trip the parser is designed for, and /*/ shows up in real stylesheets as a comment-toggle hack.

Root cause

In lib/parse.js the closing delimiter is located with:

next = value.indexOf("*/", pos);

pos points at the opening /, so the search range includes the opening /*. For /*/, indexOf("*/", 0) finds a */ at index 1 — i.e. it reuses the * of the opening /* as the * of the closing */. The comment is then treated as closed with empty content.

Fix

Start the search past the opening delimiter so the two *s can't overlap:

next = value.indexOf("*/", pos + 2);

Now /*/ has no */ after the opening, so it is correctly an unclosed comment with content /. Already-closed comments are unaffected: /**/, /*c*/, /****/ still find their real closing */.

Test plan

• New parse test: /*/ parses to { type: "comment", value: "/", unclosed: true } (fails on main).
• Round-trip cases added to the i/o test (/*/, a /*/ b, /*/ comment hack /**/).
• A property check over 300k generated CSS values found this as the only round-trip divergence; it drops to zero with the fix. Full suite green (node --test), oxlint/oxfmt clean.