Morphology: glue chapter keeps htmlSplit := .never and its sections lack file := #46

CSwL/Morphology.lean is a glue chapter: it gathers FinnishVowelHarmony, SwedishPlural and Phonemes from CSwL/Morphology/ via {include 1 …}. But it sets htmlSplit := .never, and none of the three sections sets file :=.

STYLE-CODE.md (the paragraphs on glue chapters, htmlSplit and file :=) asks a glue chapter to omit htmlSplit := .never, so that each section gets its own page, and asks each section for a file := key that matches its module name, so that it becomes its own module in the generated project. As it stands, the three sections share one HTML page and are merged into a single generated CSwL/Morphology.lean.

Suggested fix, as done for Parsing in #45:

• drop htmlSplit := .never from CSwL/Morphology.lean;
• add file := "FinnishVowelHarmony", file := "SwedishPlural" and file := "Phonemes" to the sections;
• run make all and check that the generated projects still build, since the extractor resolves the chapter's imports against the generated module names.