add timestamp to dirmd files

README.md

@@ -142,6 +142,7 @@ Example output with `dirmd -o docs.md ~/repos/myproject --vertical-slices`:
 
 Output is designed for RAG ingestion and LLM context windows, not human presentation:
 
+- **ISO 8601 Timestamp**: Added as a metadata line (`> Generated: ...`) immediately after the H1 header for every new file created.
 - **ASCII tree format** (`+-` instead of Unicode box-drawing) to reduce token overhead
 - **Explicit file delimiters**: `--- FILE: ./path (bytes, lines) ---` and `--- END FILE ---`
 - **Document type markers**: `[ROOT]` and `[SLICE]` in H1 headers
@@ -218,15 +219,17 @@ For full documentation on the Proton Drive CLI, including installation, authenti
 Produces markdown with:
 
 1. Absolute path as H1 header with `[ROOT]` or `[SLICE]` marker
-2. ASCII directory tree (indented with `+-` and `|` characters)
-3. Vertical slices index table (sliced mode only)
-4. All text files with content in fenced code blocks
-5. Explicit `--- FILE: ---` and `--- END FILE ---` delimiters with byte and line counts
-6. Language detection from file extensions
+2. **Timestamp metadata line** (ISO 8601) immediately after the H1 header (only for new files)
+3. ASCII directory tree (indented with `+-` and `|` characters)
+4. Vertical slices index table (sliced mode only)
+5. All text files with content in fenced code blocks
+6. Explicit `--- FILE: ---` and `--- END FILE ---` delimiters with byte and line counts
+7. Language detection from file extensions
 
 Example output structure (non-sliced mode):
 
     # /home/user/repos/myproject [ROOT]
+    > Generated: 2026-09-02T14:30:00Z
 
     ## Directory Tree