docs: Eigene Endung .werkbaum + fünf Beispieldateien unter docs/examples/

Mit nur einem Beispiel ließ sich das Umschalten zwischen Dokumenten (D22)
nicht zeigen — jeder ?sourceUrl=-Link legt genau ein Dokument an (D23), erst
mehrere nacheinander geöffnete füllen den Wähler.

- Neue Endung `.werkbaum` (D24, SPEC §12): macht Notationstexte zuordenbar
  (spätere Editor-Zuordnung, Syntax-Highlighting, Öffnen/Speichern). Konvention,
  kein Vertrag — `?sourceUrl=` wertet weder Endung noch Content-Type aus, `.txt`
  bleibt gültig. `.gitattributes` führt `*.werkbaum` als Text (LF).
- docs/example-plan.txt -> docs/examples/example-plan-0.werkbaum (Inhalt bis
  auf die Kopfzeile unverändert); README-Links nachgezogen.
- Neu, je einen anderen Aspekt zeigend:
  example-plan-1 (Küche: kein Software-Plan, alternativenlastig — günstigster
  Pfad), example-plan-2 (Konferenz: breiter Fächer, viele Beteiligte),
  example-plan-3 (drei Wurzeln = drei Bäume nebeneinander, dazu ein Knoten
  ohne Größe für das implizite-M-Badge),
  example-werkbaum (Werkbaum selbst: Bestand + mögliche Weiterentwicklung,
  destilliert aus ROADMAP/TASKS/DECISIONS).
- README.md / README.de.md: Tabelle mit den fünf Live-Links samt Hinweis, dass
  sie nacheinander geöffnet den Dokument-Wähler füllen.

Verifiziert: alle fünf parsen headless ohne Warnungen und ohne gemischte Gates
(19/26/43/28/79 Knoten, 3 Wurzeln in Beispiel 3); Vitest 34/34 grün.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/examples/example-werkbaum.werkbaum

@@ -0,0 +1,82 @@
+%% Werkbaum, planned with Werkbaum — what exists today and where it could go.
+%% Distilled from docs/ROADMAP.md, docs/TASKS.md and docs/DECISIONS.md.
+
+[~] Werkbaum (XXL) https://github.com/mhoennig/werkbaum
+  - [^] Notation (L)
+    - [^] Line format (M)
+      - [^] Status box, eight states (S)
+      - [^] T-shirt size and the "decompose from M" rule (S)
+      - [^] People tags, bare URLs, %% comments (XS)
+    - [^] And/or decomposition (S)
+    - [-] A separate storage format for the structure (L)  %% the text is the format
+    - [ ] Ticket references #123 (S)
+    - [?] Benefit per node, not only cost (M)
+      | [?] Another sigil next to the size (S)
+      | [?] Story points behind the T-shirt sizes (M)
+  - [~] Editor (XL) https://werkbaum.javagil.de
+    - [^] Live diagram from text (M)
+      - [^] Parser (S)
+      - [^] Renderer, three layout modes (M)
+        - [^] Horizontal fan (S)
+        - [^] Vertical, transposed (S)
+        - [^] Compact (S)
+    - [^] Cheapest path (M)
+      - [^] Cost model, missing size counts as M (S)
+      - [^] Metro-map line through the leaves (S)
+    - [^] Export (M)
+      - [^] SVG and PNG download (S)
+      - [^] PNG to the clipboard (S)
+      - [^] Print stylesheet (XS)
+    - [^] Nine interface languages (M)
+      - [^] Translations (S)
+      - [^] Default taken from the browser (XS)
+    - [^] Accessibility: aria labels, focus order (S)
+    - [^] Works on a phone (S)
+    - [x] Several documents in one editor (M)
+      - [x] Switcher in the editor title bar (S)
+      - [x] Load a document from ?sourceUrl= (S)
+    - [ ] Open and save .werkbaum files (S)
+    - [?] A pastel colour per person (S)
+    - [?] Dates and milestones (M)
+      | [?] An attribute in the line (S)
+      | [?] A separate timeline view (L)
+  - [^] Build and delivery (M)
+    - [^] One self-contained file, bundled by Vite (S)
+    - [^] Unit tests (S)
+    - [^] Published on every push (S)
+    - [-] Deploy through a gh-pages branch (S)  %% GitHub Actions instead
+    - [-] Fonts from Google (XS)  %% self-hosted, no third-party request
+  - [ ] Backend (XL)
+    - [ ] Kotlin and Spring Boot scaffold (M)
+      - [ ] Gradle Kotlin DSL, JDK 21 (S)
+      - [ ] Health endpoint and CI (S)
+    - [ ] Documents on the server (L)
+      - [ ] Text plus metadata, no structure format (M)
+        - [ ] REST endpoints (S)
+        - [ ] Persistence (S)
+      - [ ] Share by link (S)
+    - [?] Accounts and permissions (L)
+      | [?] Single user, one token (S)
+      | [?] Log in with OIDC (L)
+  - [?] Mermaid plugin (XL)
+    - [!] A layout engine of its own (XL)  %% measure, place, route — the real work
+      - [ ] Measure node sizes (M)
+        - [ ] Text metrics without a browser (S)
+        - [ ] Badges and tags inside the box (S)
+      - [ ] Place nodes and route connectors (L)
+        - [ ] All-of fan (M)
+          - [ ] Horizontal (S)
+          - [ ] Transposed (S)
+        - [ ] Any-of rail (S)
+    - [?] Registration with Mermaid (M)
+      | [?] External diagram, self-hosted pages only (M)
+      | [?] Pull request into Mermaid itself (L)
+  - [?] Tracker integration (XL)
+    | [?] Taiga (L) https://taiga.io
+      - [ ] Resolve #123 over the REST API (M)
+        - [ ] Read title, link and status (S)
+        - [ ] Map the workflow onto the states (S)
+      - [?] Write the status back (M)
+      - [-] A plugin inside Taiga itself (L)  %% legacy frontend, self-hosted only
+    | [?] Tenzu, the successor (XXL) https://tenzu.net
+    | [ ] No tracker, plain text is enough (XS)