Styles: simplify algorithm markup, improve step & dfn visibility

[inexorabletash]

• Bikeshed styles W3C spec substeps (and sub-substeps, etc) with bars to make the indentation level clearer. The explicit markup used for class=algorithm-steps was preventing the selector from matching. Simplify the markup and CSS to get more by doing less.

• The default <summary> element style is bold, which was making the specific definition within an algorithm's intro difficult to see. Override this for algorithms, so that the defined algorithm name "pops" more.

• Recently introduced broadcast algorithms weren't using the <details> / <summary> markup. Apply this to match the rest of the spec.

• Remove now-unused CSS validusage and informalsteps styling.

No content changes.

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Preview | Diff

[inexorabletash]

@zolkis - can you take a look? There may be history around these styles/markup that I'm missing that merits keeping them.

[inexorabletash]

While I'm here (but this question shouldn't hold up this PR)...

@zolkis the CSS for internal slots sets it up for a watermark like "Algorithm" has but there's no .internal-slots::after { content: ... } rule that actually provides the watermark text. Do you know if that was intended in 1c894021d30ef70c9ecdfbe79b4961c483fc7581 but lost somehow?

[zolkis]

the CSS for internal slots sets it up for a watermark like "Algorithm" has but there's no .internal-slots::after { content: ... } rule that actually provides the watermark text. Do you know if that was intended in 1c89402 but lost somehow?

Right, it's missing - the intent was to make internal slots stand out in a similar way, though now we should check if we still want that. BTW I will be on holiday for a week, with sparse internet, so apologies in advance if replies will come late.

[inexorabletash]

the intent was to make internal slots stand out in a similar way, though now we should check if we still want that

If the editors want to weigh in:

vs:

Literally a one line change, so easy to slip in:

@@ -116,6 +116,7 @@
 .internal-slots::after {
+    content: "Internal Slots";

[inexorabletash]

@huningxin - please merge when you're ready.

[huningxin]

@inexorabletash Please help resolve the merge conflicts and I'll merge. Thanks!

[inexorabletash]

@huningxin - resolved!