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/INDEX.md

@@ -0,0 +1,21 @@
+# Ergaenzung — Supplementary Practice Books Index
+
+These are the Hueber *Deutsch üben* practice books, used alongside
+*Menschen* A1.1 (not a replacement for it). They're organized by their own
+topic/unit structure, not by Menschen Lektion — see the "Relates to
+Menschen Lektion(en)" column below to cross-reference.
+
+## Wortschatz & Grammatik A1 (`wortschatz-grammatik-a1/`)
+
+| Einheit | Title/Topic | Relates to Menschen Lektion(en) | Status |
+|---|---|---|---|
+
+## Hören & Sprechen A1 (`hoeren-sprechen-a1/`)
+
+| Einheit | Title/Topic | Relates to Menschen Lektion(en) | Status |
+|---|---|---|---|
+
+## Lesen & Schreiben A1 (`lesen-schreiben-a1/`)
+
+| Einheit | Title/Topic | Relates to Menschen Lektion(en) | Status |
+|---|---|---|---|

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").

README.md

@@ -25,6 +25,12 @@ A1.1/
   INDEX.md        ← one-line summary of every lesson so far
 A1.2/             ← added once I move on to the next book
   ...
+Ergaenzung/       ← supplementary practice books (see below)
+  wortschatz-grammatik-a1/
+  hoeren-sprechen-a1/
+  lesen-schreiben-a1/
+  _template.md
+  INDEX.md
 scripts/
   transcribe.py   ← local ASR fallback (faster-whisper) for audio with no
                      official transcript
@@ -85,3 +91,32 @@ given track, e.g. supplementary listening material):
 
 Copy the `A1.1/` folder structure (minus content) into a new `A1.2/` folder
 and repeat the process.
+
+## Supplementary practice books (`Ergaenzung/`)
+
+Alongside *Menschen*, I also use three Hueber *Deutsch üben* practice
+books: **Wortschatz & Grammatik A1**, **Hören & Sprechen A1**, and **Lesen
+& Schreiben A1**. Unlike *Menschen*, these aren't organized lesson-by-lesson
+against a shared story/curriculum — each is structured around its own
+topics/units (grammar points for Wortschatz & Grammatik, skill-practice
+units for the other two). Forcing them into the `A1.1/lektion-XX.md`
+structure would misrepresent that, so they get their own space instead:
+
+```
+Ergaenzung/
+  wortschatz-grammatik-a1/einheit-XX.md
+  hoeren-sprechen-a1/einheit-XX.md
+  lesen-schreiben-a1/einheit-XX.md
+  _template.md   ← template for these files
+  INDEX.md       ← per-book tables mapping each unit to Menschen Lektion(en)
+```
+
+Each `einheit-XX.md` is scoped like a lesson file (vocab/grammar covered,
+exercise summary, audio transcript if applicable, answer key highlights,
+notes) but adds a **"Relates to Menschen Lektion(en)"** field so a tutor
+session can tell whether content is reinforcing what's already been covered
+in *Menschen* or introducing something new/out-of-scope.
+
+Workflow for adding a unit: same as adding a *Menschen* lesson (get the
+pages as PDF/photo, Claude summarizes into `einheit-XX.md` using
+`Ergaenzung/_template.md`, review, update `Ergaenzung/INDEX.md`, commit).