Switch demo font to DejaVu Sans Mono; fix fonts package name in CI

Monaco is macOS-only and falls back badly on Ubuntu runners.
DejaVu Sans Mono is provided by fonts-dejavu-core and renders
consistently across both platforms.

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

Author: gkthiruvathukal

.github/workflows/release.yml

@@ -26,7 +26,7 @@ jobs:
       - name: Install ffmpeg and fonts
         run: |
           sudo apt-get update -q
-          sudo apt-get install -y ffmpeg fonts-liberation fonts-dejavu-mono
+          sudo apt-get install -y ffmpeg fonts-dejavu-core
 
       - name: Install vhs and ttyd
         run: |

demos/dll-dark.tape

@@ -5,7 +5,7 @@ Output demos/dll-dark.mp4
 
 Set Theme "TokyoNight"
 Set FontSize 16
-Set FontFamily "Monaco"
+Set FontFamily "DejaVu Sans Mono"
 Set Width 1800
 Set Height 900
 Set Framerate 30

demos/dll-light.tape

@@ -5,7 +5,7 @@ Output demos/dll-light.mp4
 
 Set Theme "Catppuccin Latte"
 Set FontSize 16
-Set FontFamily "Monaco"
+Set FontFamily "DejaVu Sans Mono"
 Set Width 1800
 Set Height 900
 Set Framerate 30