Tidy-up pass over theorems/proofs

[rolyp]

Consolidation pass before next Thursday’s meeting.

• separate clause lemma for list-rest patterns
• check each proof for consistency with \eq handling in associated definitions
• each proof to reference the theorem (part) it proves
• each theorem to forward reference the relevant proof (but see Anonymised paper build omitting appendices #104)
• restate the theorem before the proof? (see objects-as-automata for how to do this)
• reduce space around \intertext{\crossrule}?
• standardise on use of parentheses and capitalisation in rightmost column
• upload new version to arXiv