DOCX template contract

The preferred insertion point is a Content Control with tag or title DOC_BODY, then a bookmark named DOC_BODY, then the exact marker {{DOC_BODY}}. If none is present, generation fails explicitly; the body is never silently appended.

The template is copied to a temporary working file. Body headers/footers are not imported. Template sections and headers/footers are retained, fields are updated, and Word repaginates before saving.