fix: land quoted-text fallback fix on main (PR #20 follow-up) - #21

Review follow-up for #19: `opencode run "/loop 5m"` stores the user
message with literal outer quotes (argv elements containing spaces are
re-quoted), so the fallback regex /^\/loop.../ never matched real
run-mode text and every deterministic guard was still bypassed
end-to-end — the unit tests only simulated unquoted parts.

- reuse stripOuterQuotes (now exported) before matching, mirroring
  handleUserCommand
- scan remaining text parts instead of bailing on the first non-match
- regression tests for double- and single-quoted command text and for
  /loop appearing in a later text part (12/12 run-mode tests, 176/176
  overall, tsc clean)
- verified end-to-end against a real `opencode run` with the built
  plugin: quoted cron input is now rejected deterministically and no
  task is created; a quoted valid interval creates the fixed task

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>