feat(tools): mirror-docs — Liste geteilter Dokumente per Timer nach git spiegeln (D88-Nachtrag 3)

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

docs/examples/werkbaum.werkbaum

@@ -151,6 +151,7 @@
     - [~] #col.git: Git as the shared store (L)
       | [ ] #col.git.pr: A file in a repository, changed by pull request (S)  %% works today, no code
       | [^] #col.git.pull: A script pulls the server document and commits it (S)  %% tools/pull-doc --git-commit, dated commits — see D88
+        - [x] #col.git.timer: A timer on the backend host mirrors a list of documents into a branch (S)  %% tools/mirror-docs, systemd timer — see D88-Nachtrag 3
       | [?] #col.git.auto: The backend commits every change (L) :#be.scaffold
         - [?] #col.git.hist: History and restore (M)
           - [?] #col.git.diff: Diff between two versions (S)
@@ -970,6 +971,13 @@
   worktree — date, title and version in the message, no commit when nothing
   changed. Run from cron, a shared plan archives itself.
 
+#col.git.timer
+  tools/mirror-docs reads a list of documents (uuid and path), runs pull-doc
+  --git-commit for each and pushes once. As a systemd timer on the backend host
+  it mirrors the shared plans every 15 minutes into a werkbaum-mirror branch —
+  the net outside the browser and outside the backend, running whether or not
+  anyone remembers.
+
 #col.git.auto
   The server turns every change into a commit. History, restore and branches
   follow from that, with commit granularity as the open question.