Rename default branch from master to main

Update GitHub Actions workflow, skill files, and shell scripts
to reference 'main' instead of 'master'.

.claude/skills/sync-site/SKILL.md

@@ -75,5 +75,5 @@ Stage, commit, and push the change:
 ```bash
 git add site/index.qmd
 git commit -m "Sync site/index.qmd with README.md"
-git push origin master
+git push origin main
 ```

.claude/skills/update-pypi-dates/SKILL.md

@@ -51,7 +51,7 @@ If any updates were made:
 ```bash
 git add README.md non-github-urls.md
 git commit -m "Update PyPI project last updated dates"
-git push origin master
+git push origin main
 ```
 
 ## Usage

.claude/skills/update-pypi-dates/scripts/update_pypi_dates.sh

@@ -19,7 +19,7 @@ if [ $exit_code -eq 0 ]; then
         echo "📝 Changes detected, committing..."
         git add README.md
         git commit -m "Update PyPI project last updated dates"
-        git push origin master
+        git push origin main
         echo "✅ Changes pushed to remote"
     fi
 fi

.github/workflows/build.yml

@@ -4,7 +4,7 @@ on:
   schedule:
     - cron: "0 1 * * *"
   push:
-    branches: [ master ]
+    branches: [ main ]
     paths:
       - 'README.md'
       - 'parse.py'