docs: maintain-the-wiki names the synced-folder backup for an instance without a git server, and what a failed machine-data backup after a push means (#186 close)

Files changed:
- docs/how-to/maintain-the-wiki.md

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SnAJ7Z3CpVD3PRbN73QtU2

docs/how-to/maintain-the-wiki.md

@@ -58,7 +58,12 @@ tools/wikitool sources trace --page "HA Integration"    # which raw files this p
   needs. A refusal usually means the task should be split, not pushed through.
 - **No reachable remote.** Without `--no-push`, `publish` refuses with exit 1 before committing when
   the remote is not configured or cannot be reached. An instance that is meant to stay local passes
-  `--no-push` on every publish.
+  `--no-push` on every publish - or, without a git server, pushes to a synced folder instead:
+  [back-up-to-a-synced-folder.md](back-up-to-a-synced-folder.md).
+- **A failed machine-data backup.** With a backup into a synced folder, a publish that pushed also
+  copies this machine's files that are not in git. If that copy fails, `publish` prints a `WARN`
+  line and still succeeds - the commit and the push stand. Fix what the line names, then run
+  `tools/wikitool backup run`; another publish does not repeat the copy.
 
 Every gate, and which command it belongs to: [exit codes and gates](../reference/exit-codes.md).
 Why they are enforced in code: [why-gates-are-code.md](../explanation/why-gates-are-code.md).