Handle objects with null prototypes as topics

[strugee]

See the inline comment - impetus here is that if you require() an ES6 module, you get an Object with its prototype set to null, which results in this crash:

[snipped]
  vows:batch Beginning topic of batch 'When we get the conference space planner module' +0ms
  vows:batch Completed topic of batch 'When we get the conference space planner module' +17ms
  vows:batch Results of topic of batch 'When we get the conference space planner module' defined and not a Promise; running sync +0ms
  vows:at-most-once First call of atMostOnce() wrapper of bound () +17ms
/var/home/alex/Development/patch/node_modules/vows/lib/batch.js:164
      debug(`Results for topic of '${this.title}': ${err}, ${results.join(', ')}`)
                                                                     ^

TypeError: Cannot convert object to primitive value
    at Array.join (<anonymous>:null:null)
    at Batch.<anonymous> (/var/home/alex/Development/patch/node_modules/vows/lib/batch.js:164:70)
[snipped]

Because there's no toString on the module object, type coercion fails.

[strugee]

Tests passing locally for me under Node 24

[strugee]

Rebasing on #413 to get CI coverage of our supported versions.

[strugee]

Marking as draft since I'm experiencing related crashes in SeaGL/patch and am unsure if this is a full fix.