Bash parameter-expansion safety checks tightened, gated by tengu_shimmying_mochi

The analyzer that judges whether a shell command's variable expansions are safe or need extra scrutiny now refuses two more patterns: ${!...} forms used for name-listing or positional parameters, and ${ |...} patterns. It also added a stricter "canonical form" check, requiring that the parsed pieces of an expansion reconstruct the original text exactly before it's treated as safe.