Scaffold Ergaenzung/ for supplementary practice books

Adds structure for the three Hueber Deutsch üben books (Wortschatz &
Grammatik, Hören & Sprechen, Lesen & Schreiben A1), kept separate from
the Menschen A1.1 lesson files since they're organized by topic/unit
rather than a shared lesson curriculum.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Ergaenzung/_template.md

@@ -0,0 +1,45 @@
+# [Book] — Einheit XX: [Title/Topic]
+
+Pages: [XX–YY]
+
+## Overview
+
+- Skill focus: [Wortschatz / Grammatik / Hören / Sprechen / Lesen / Schreiben]
+- Topic: [grammar point or theme covered in this unit]
+- Relates to *Menschen* Lektion(en): [e.g. L5, L6 — where this overlaps with
+  the main course book; "new" if it goes beyond what Menschen A1.1 covers]
+
+## Vocabulary / Grammar covered
+
+Only list what's actually new or drilled here — skip anything that just
+repeats a Menschen lesson's Lernwortschatz without adding to it.
+
+### [Category / grammar point]
+| German | English | Notes |
+|---|---|---|
+
+## Exercise summary
+
+Brief summary of what each exercise practices — not full instructions or
+full exercise text.
+
+1. [skill practiced]
+2. ...
+
+## Audio / Listening (if applicable — Hören & Sprechen only)
+
+Transcript source: Official / ASR (see repo README for the audio workflow).
+
+```
+[dialogue transcript]
+```
+
+## Answer key highlights
+
+Selected answers useful for self-checking or for Claude to verify answers
+against — not necessarily exhaustive.
+
+## Notes / gotchas
+
+- Anything tricky, exceptions, or scope warnings (e.g. "goes beyond A1.1
+  vocab — flag before using in exercises with content past Lektion N").