Add GitHub Actions deployment workflow to S3

[replakcan]

Description

Create a GitHub Actions workflow that deploys the static build output to S3 when changes are merged into main.

Scope

• Create deployment workflow
• Run deployment only on push to main
• Build the static site
• Sync out/ directory to S3
• Delete removed files from S3 using sync delete behavior
• Use GitHub secrets for deployment configuration

Out of Scope

• CloudFront invalidation
• Custom domain
• Preview environments
• Multi-environment deploys

Acceptance Criteria

• Deployment workflow exists
• Workflow runs only on push to main
• Static build is generated before deploy
• out/ directory is synced to S3
• Removed files are deleted from S3
• Deployment fails if build fails
• AWS credentials are not hardcoded

Technical Notes

• Prefer GitHub OIDC over long-lived AWS access keys.
• Use aws s3 sync out s3://bucket-name --delete.

Related

• Depends on: Add GitHub Actions CI workflow
• Depends on: Create S3 bucket for static site files