Revise functions notes to the literate memoir pattern

[dbosk]

Part of the notes-revision effort (see the tracking issue for the full
per-deck workflow: literate contents.nw conversion, memoir notes,
narrative prose, pedagogical restructuring, \ltnote{} annotations,
LaTeX semantics, LO labels, review).

Misconceptions input: functions-variables.tex (arguments, scope, argument order — also covers default parameters, relevant to the slides-default deck) in vt-prog-misconceptions — documented
misconceptions with critical-aspect analyses and variation patterns to
design activities against (per-deck workflow step 5 in the tracking
issue); matching diagnostic item bank quiz-funcvars-{start,end}.json.

Decks

modules/functions/slides-builtins

• Literate conversion (contents.nw, chunks replace \inputminted
  line ranges, Makefile + gitignore)
• Memoir notes.tex
• Narrative prose (notes read standalone)
• Pedagogical restructuring (try-first, examples first, variation
  theory)
• \ltnote{} annotations + ltnotes.bib
• LaTeX semantics pass
• Mnemonic LO labels in abstract.tex
• Build + review pass

modules/functions/slides-recursion

• Literate conversion (contents.nw, chunks replace \inputminted
  line ranges, Makefile + gitignore)
• Memoir notes.tex
• Narrative prose (notes read standalone)
• Pedagogical restructuring (try-first, examples first, variation
  theory)
• \ltnote{} annotations + ltnotes.bib
• LaTeX semantics pass
• Mnemonic LO labels in abstract.tex
• Build + review pass

modules/functions/slides-generators

• Literate conversion (contents.nw, chunks replace \inputminted
  line ranges, Makefile + gitignore)
• Memoir notes.tex
• Narrative prose (notes read standalone)
• Pedagogical restructuring (try-first, examples first, variation
  theory)
• \ltnote{} annotations + ltnotes.bib
• LaTeX semantics pass
• Mnemonic LO labels in abstract.tex
• Build + review pass