feat: classify 2026Q3 new contributors by first contribution type - add first-contribution-type distribution table (merged PR 7 / valid issue 56 / review & answer 2 / others 37, total 102) - group the welcome list by first contribution type; highlight 6 PR+issue dual-first contributors - congratulate @tjh9527 (27 PRs + 29 issues) and @z2036709353 (46 issues + 6 PRs) on reaching the Bronze milestone in their first quarter - fix new-contributor criteria wording in Section A (code contribution -> actual contribution) Signed-off-by: hl1hl <1782518783@qq.com>