str.splitlines() also splits on Unicode line separators (U+2028, U+2029)
which are valid inside JSON string values without escaping. When an open
GitHub issue title or body contained one of these characters, the
duplicate-issue check script broke the gh output mid-string and crashed
with 'Unterminated string ...' before the auto-close path could run.
gh api --paginate for an array endpoint already concatenates pages into
a single JSON array, so just parse the whole stdout once. Add a
regression test covering U+2028/U+2029 and the existing PR-filter path.
Co-authored-by: Krrish Dholakia <krrish-berri-2@users.noreply.github.com>
