fix(codex): avoid two-line grep -c count breaking record-session integer test

[lmncaj]

Summary

• codex-record-session.sh counts candidate thread ids with [ "$(grep -c . "$tids_file" 2>/dev/null || echo 0)" -eq 1 ]. On zero matches grep -c prints 0 and exits 1, so the fallback stacks a second 0 and the test dies with [: 0 / 0: integer expected — on every actas in a cwd with no matching Codex rollout.
• Capture the count first (|| true) and default only the no-stdout case (${tid_count:-0}, missing/unreadable file). The 1-match and ambiguous >1 behaviors are unchanged.
• Regression test: the zero-match case stays silent and exits 0. Fails on the old code. No other grep -c … || echo combinations remain in the repo.

Test plan

• bats tests/test_codex_resume.bats — 10/10
• bash -n scripts/drivers/types/codex/codex-record-session.sh, git diff --check clean