CI/CD optimization and repository health improvements

[andreion1ca]

Description:

This issue tracks workflow optimizations and repository-level improvements. The primary goal is reducing MAC37 queue time and cleaning up committed artifacts.

runs-at-night.yml

• No functional changes needed — file is fully commented out; either restore it or delete it to avoid dead-code confusion

deploy-docs-to-staging.yml

• Delete workflow file entirely

push.yml

• Restrict to run only on auto-update branches (currently fires on every push to every branch, including auto-update branches created by transfer_to_open_source.yml in the closed-source repo)
• [TBD] Move Roslyn-Analyzer-dotnet job from MAC37 to a Windows runner — it only needs dotnet, not macOS
• [TBD] Move copyright job from MAC37 to a Windows runner — it only runs a PowerShell script
• Add timeout-minutes: 60 to all build/test jobs
• Add actions/cache for Library/ keyed on Assets/**, Packages/**, ProjectSettings/** — currently every run reimports Unity assets from scratch

Runner Distribution

• Change all runs-on: [self-hosted, MAC37] to runs-on: [self-hosted, macOS] for jobs that don't require Mac37 specifically — this allows Mac36 to share the load

Repository Hygiene

• Remove committed .DS_Store files — listed in .gitignore but committed before the rule was added; run git rm --cached $(git ls-files -i --exclude-standard) and commit
• Remove committed .venv/ directory — a full Python virtual environment is tracked in source control; run git rm -r --cached .venv/
• Verify Library/ folder is not tracked — it exists in the working tree; confirm it is fully excluded by the .gitignore
• Make sure that there is a single file as source of truth for version
• Standardize issue templates to match the shared template set