fix: draw command in @penrose/automator

[wodeni]

Description

Fixes #935

The draw command in @penrose/automator calls singleProcess with the wrong arguments, notably missing variation. This PR adds an optional --variation option to the command and generate a random string for the variation seed if none is provided.

Examples with steps to reproduce them

See #935

Checklist

• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new ESLint warnings
• I have reviewed any generated changes to the diagrams/ folder

[codecov]

Codecov Report

Merging #937 (13383af) into main (40788cc) will not change coverage.
The diff coverage is n/a.

❗ Current head 13383af differs from pull request most recent head bd48fa2. Consider uploading reports for the commit bd48fa2 to get more accurate results

@@           Coverage Diff           @@
##             main     #937   +/-   ##
=======================================
  Coverage   68.15%   68.15%           
=======================================
  Files          62       62           
  Lines        8123     8123           
  Branches     1771     1771           
=======================================
  Hits         5536     5536           
  Misses       2580     2580           
  Partials        7        7           

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