Sækja usage 7.1.2

Fixed
- (complete) Completion candidates and extension filters are now handled as plain text in every shell (#1581, @jdx):
- bash: usage generate completion bash used to pass candidates through compgen -W, which expands them as shell input. A run= completer that printed $(touch pwned) ran that command when you pressed Tab, and a * candidate turned into the files in the current directory. The completion-init handler had the same globbing problem. Both now read one candidate per line without expanding it, so a candidate that contains a space stays one entry instead of splitting in two.
- zsh: extension names were inserted directly into the _files -g pattern, and zsh runs glob qualifiers as code. The pattern is now built only from plain extension names (letters, digits, _ . + -). If no usable names are left, completion falls back to unfiltered _files. This also fixes a single extension, which produced *.(toml) and matched nothing. It now produces *.toml.
- fish: extensions are matched as a literal suffix, so a * or ? in an extension no longer matches extra files.

Changed
- (complete) A command brought in by mount now uses only the completers it declares itself, in its own complete nodes or inside its arg nodes (#1581, @jdx). Before, a mounted argument that shared a name with a top-level completer (for example <tool>) used the mounting spec's completer, even when the mounted command declared its own. If you type one of the mounting CLI's flags inside a mounted command, its value still completes the same way it does outside the mount. Specs without mounts are unaffected. If a mounted command relied on a top-level completer, declare it in the spec that the mount emits instead, for example with complete "tool" run="..." inside the cmd.