fix(codegen): verify U+2028/U+2029 sourcemap panic fix is correct

[Copilot]

Addresses a review concern that the LS/PS sourcemap panic fix in #19548 may have been reviewed against an older, unpatched version of the code.

Verification

Confirmed the current update_generated_line_and_column implementation correctly handles LS (U+2028) and PS (U+2029) — the LS_OR_PS_FIRST_BYTE branch returns 3 as line_break_byte_len, advancing both line_start_index and idx past all 3 bytes of the sequence. This prevents from_utf8(&output[line_start_index..]) from receiving a slice starting mid-codepoint and panicking.

The test cases added in #19548 exercise the fix:

create_mappings("\u{2028}", 1, 0);
create_mappings("\u{2029}", 1, 0);
create_mappings("a\u{2028}b", 1, 1);
create_mappings("a\u{2029}b", 1, 1);
create_mappings("`\u{2028}`", 1, 1);
create_mappings("`\u{2029}`", 1, 1);

All 9 sourcemap_builder tests pass.

---

🔒 GitHub Advanced Security automatically protects Copilot coding agent pull requests. You can protect all pull requests by enabling Advanced Security for your repositories. Learn more about Advanced Security.