Lint #USAGE field ordering

[junior-ricon]

Problem

#USAGE directive fields are hand-written across mise tasks, and field ordering is easy to drift. In KnickKnackLabs/shell#12, Or noted that a directive like:

#USAGE arg "input" default="" help="Input to send" var=#true

would be more readable/consistent with structural fields earlier, e.g. var=#true before prose help, and likely before default="" as well.

Proposal

Add a codebase lint rule for #USAGE field ordering in mise task comments.

Possible canonical ordering, to refine while implementing:

1. directive kind / name, e.g. arg "input" or flag "--raw"
2. structural parser fields, e.g. var=#true
3. defaults / value metadata, e.g. default=""
4. human-facing prose, e.g. help="..."

Notes

• The rule should probably start as autofixable or at least produce a clear expected-order diagnostic.
• It should avoid changing quoted strings or directive semantics.
• Source prompt: Or review comment on KnickKnackLabs/shell#12.