feat(config): enable swatch by default for desktop mode

Set swatch = true as the default in the stock [desktop] configuration
and internal defaults. This ensures that desktop notifications include
a visual color swatch by default. Updated README and tests accordingly.

README.md

@@ -106,6 +106,7 @@ json   = false  # copy JSON format instead of plain text
 name   = false  # fetch color name (requires network)
 copy   = true   # copy result to clipboard
 notify = true   # show desktop notification with the copied value
+swatch = true   # show color swatch in notification
 ```
 
 You can also use the CLI to manage your configuration:

color-tool

@@ -45,7 +45,7 @@ desktop_name=0
 desktop_notify=1
 desktop_copy=1
 desktop_output="hex"
-desktop_swatch=0
+desktop_swatch=1
 
 # Track which settings were explicitly set via CLI flags to ensure they override config
 cli_json=""
@@ -274,7 +274,7 @@ json   = false  # copy JSON format instead of plain text
 name   = false  # fetch color name (requires network)
 copy   = true   # copy result to clipboard
 notify = true   # show desktop notification with the copied value
-swatch = false  # show color swatch in notification
+swatch = true   # show color swatch in notification
 EOF
 }