fix: avoid apostrophe in fm-brief.sh heredoc nested in command substitution

[Seangee86]

Summary

• bin/fm-brief.sh crashes with unexpected EOF while looking for matching \'''on macOS's default bash (3.2.57) when scaffolding a ship brief for ano-mistakes`-mode project.
• Root cause: macOS ships bash 3.2, which mis-parses a literal apostrophe inside a heredoc when that heredoc is nested inside a $(...) command substitution (reproduced independently outside this repo; a standalone top-level heredoc with the same apostrophe is fine, only the nested-in-$() case breaks).
• The no-mistakes-mode DOD heredoc (DOD=$(cat <<EOF ... EOF)) in the ship-brief case block contains the word "firstmate's", which trips this.
• Fix: reworded that one line to drop the apostrophe ("firstmate's authority check" -> "the firstmate authority check"). No behavior change, no other heredocs in the file are affected (verified none of the other apostrophes in the file sit inside a heredoc nested in $(...)).

Test plan

• bash -n bin/fm-brief.sh passes (previously failed with the EOF/quote error)
• bin/fm-brief.sh <id> <repo> (no-mistakes mode) scaffolds successfully end to end

[kunchenguid]

thanks for tracking this down. i merged #1093, which fixes the same macOS bash 3.2 parse failure - it removes the command substitution around those heredocs instead of rewording the apostrophe, so i'm closing this one as superseded. appreciate the help here.