update doc reference and test [gh-pahes] build trigger

Author: kovaca

docs/src/content/docs/export-formats/gdal.mdx

@@ -15,36 +15,49 @@ The GDAL exporter creates text files compatible with GDAL's `gdaldem color-relie
 
 ## Output Format
 
-The output is a text file with one color entry per line:
+The output is a text file with one color entry per line. By default, the output includes a nodata (`nv`) line but no comments:
+
+```
+nv 0 0 0 0
+0.0 68 1 84 255
+1.0 68 2 85 255
+2.0 68 3 87 255
+...
+255.0 253 231 37 255
+```
+
+When using verbose mode (`-v`), comments are included:
 
 ```
 # GDAL Color Relief File generated by Palettize
 # Colormap name: viridis
 # Domain: [0, 255], Scaler: linear
 # Interpolation Space for Colormap: oklch
-# Uncomment next line for default nodata transparency
-# nv 0 0 0 0
+nv 0 0 0 0
 0.0 68 1 84 255
-1.0 68 2 85 255
-2.0 68 3 87 255
 ...
-255.0 253 231 37 255
 ```
 
 Each line has the format: `value R G B A`
 
 ## CLI Usage
 
 ```bash
-# Basic export
+# Basic export (includes nv line by default)
 palettize create viridis --format gdal --output viridis.txt --domain 0,255
 
+# With verbose comments
+palettize create viridis -f gdal -o viridis.txt --domain 0,255 -v
+
 # Custom number of colors
 palettize create viridis -f gdal -o viridis.txt --domain 0,255 --steps 256
 
-# With nodata handling
+# Without nodata line
+palettize create viridis -f gdal -o viridis.txt --domain 0,255 -O nodata=false
+
+# Custom nodata value
 palettize create viridis -f gdal -o viridis.txt --domain 0,255 \
-  -O nodata_value=nv -O nodata_color="0,0,0,0"
+  -O nodata_value=-9999 -O "nodata_color=0,0,0,0"
 ```
 
 ## Python Usage
@@ -74,9 +87,10 @@ with open("viridis.txt", "w") as f:
 | Option | Type | Default | Description |
 |--------|------|---------|-------------|
 | `num_colors` | `int` | `256` | Number of color steps to generate |
-| `nodata_value` | `float \| str` | | NoData value. Use `"nv"` for GDAL keyword |
+| `nodata` | `bool` | `true` | Include `nv 0 0 0 0` line by default |
+| `nodata_value` | `float \| str` | `"nv"` | NoData value. Use `"nv"` for GDAL keyword or a numeric value |
 | `nodata_color` | `tuple[int,int,int,int]` | `(0,0,0,0)` | RGBA color for NoData |
-| `scaler_type` | `str` | | Scaler type for metadata comment |
+| `verbose` | `bool` | `false` | Include comment header lines (set automatically by `-v` flag) |
 
 ## Using with GDAL
 
@@ -93,14 +107,16 @@ gdaldem color-relief input.tif viridis.txt output.tif \
 
 ## NoData Handling
 
-GDAL supports a special `nv` keyword for NoData values:
+By default, the GDAL exporter includes an `nv 0 0 0 0` line for transparent nodata handling. GDAL's `nv` keyword applies to any nodata value defined in the raster.
 
 ```bash
-# Include NoData line in output
-palettize create viridis -f gdal -o viridis.txt --domain 0,255 \
-  -O nodata_value=nv
+# Default behavior includes nv line
+palettize create viridis -f gdal -o viridis.txt --domain 0,255
+
+# Disable nodata line
+palettize create viridis -f gdal -o viridis.txt --domain 0,255 -O nodata=false
 
-# Specify numeric NoData value
+# Specify a numeric NoData value instead of nv
 palettize create viridis -f gdal -o viridis.txt --domain 0,255 \
   -O nodata_value=-9999 -O "nodata_color=0,0,0,0"
 ```