Fix several lang-related issues

[object-Object]

See #391.

Fixes #515. Fixes #562.

May have some overlap with #609.

Not done yet:

• Document the debug cube
• Improve documentation of iota embedding
• Cost of allay quenching recipe (#617)
• Undocumented "cycle variant" spell (we're probably just going to remove this)
• Inconsistent formatting of pattern inputs/outputs

Possibly also related:

• #616
• #482 (?)
• #617
• #580
• #647
• #649