feat(opencode): support adaptive thinking for claude sonnet 4.6 (#14283)

Co-authored-by: tctev <224793535+tctev@users.noreply.github.com>
Co-authored-by: Aiden Cline <63023139+rekram1-node@users.noreply.github.com>
Co-authored-by: Aiden Cline <aidenpcline@gmail.com>