v0.7.0: add XMP sidecars

USERGUIDE.md

@@ -22,6 +22,7 @@ It is especially useful when you want to:
 - Verify that files referenced by a manifest exist on disk.
 - Detect missing, zero-byte, and size-mismatched manifest files.
 - Inspect or clear deduplicated failure records.
+- Write optional XMP sidecar metadata for archival workflows.
 - Script Photos exports with stable exit codes.
 
 It is not intended to replace Apple Photos, iCloud Photos, or Time Machine. Think of it as an additional file-based export and backup tool.
@@ -538,6 +539,25 @@ Supported tokens:
 
 Assets without parseable creation dates stay in the base output path.
 
+## XMP Sidecars
+
+Use XMP sidecars when you want portable metadata next to exported files:
+
+```bash
+./bin/photoscli export --album-id "Vacation" --out ./Vacation --sidecar xmp
+```
+
+Sidecars are disabled by default. When enabled, they use the exported file basename:
+
+```text
+IMG_0001.jpg -> IMG_0001.xmp
+IMG_0001.HEIC -> IMG_0001.xmp
+```
+
+The XMP includes photoscli archive metadata such as asset ID, original filename, exported filename, album, manifest path, media type, dimensions, favorite state, cloud state, export mode, version, exported time, size, and creation date when available.
+
+If you explicitly request `--sidecar xmp` and the XMP file cannot be written, the asset is counted as failed.
+
 ## Configuration File
 
 You can store default values in:
@@ -557,6 +577,7 @@ sort = "newest"
 media = "photos"
 retry = 3
 log = true
+sidecar = "xmp"
 ```
 
 Use a custom config path: