Add docs for updating josh-sync version in Nix devenv

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Makefile

@@ -23,7 +23,7 @@ dist/josh-sync: bin/josh-sync lib/*.sh VERSION
 	@echo '# Generated by: make build' >> dist/josh-sync
 	@echo '' >> dist/josh-sync
 	@# Inline all library modules (strip shebangs and source directives)
-	@for f in lib/core.sh lib/config.sh lib/auth.sh lib/state.sh lib/sync.sh; do \
+	@for f in lib/core.sh lib/config.sh lib/auth.sh lib/state.sh lib/sync.sh lib/onboard.sh; do \
 		echo "# --- $$f ---" >> dist/josh-sync; \
 		grep -v '^#!/' "$$f" | grep -v '^# shellcheck source=' >> dist/josh-sync; \
 		echo '' >> dist/josh-sync; \

docs/guide.md

@@ -165,6 +165,34 @@ SUBREPO_SSH_KEY="-----BEGIN OPENSSH PRIVATE KEY-----
 # AUTH_REPO_TOKEN=<auth-specific-token>
 ```
 
+### Updating josh-sync in devenv
+
+To update to the latest version:
+
+```bash
+devenv update josh-sync
+```
+
+Or with plain Nix flakes:
+
+```bash
+nix flake lock --update-input josh-sync
+```
+
+To pin to a specific version, use a tag ref in `devenv.yaml`:
+
+```yaml
+josh-sync:
+  url: git+https://your-gitea.example.com/org/josh-sync?ref=v1.1
+  flake: true
+```
+
+After updating, verify the version:
+
+```bash
+josh-sync --version
+```
+
 ### Option B: Manual installation
 
 Install the required tools, then either:

flake.nix

@@ -28,6 +28,7 @@
 
             installPhase = ''
               mkdir -p $out/{bin,lib}
+              cp VERSION $out/
               cp lib/*.sh $out/lib/
               cp bin/josh-sync $out/bin/
               chmod +x $out/bin/josh-sync