Add bilingual docs summaries and main push deploy guard

[Pigbibi]

Summary

• Add bilingual summary entry points to repository documentation.
• Keep existing detailed docs intact while adding cross-language navigation.
• Add an ENABLE_MAIN_PUSH_CLOUD_RUN_AUTOMATION guard so docs merges to main do not deploy Cloud Run unless explicitly enabled.

Validation

• Custom bilingual coverage scan: coverage_issues=0.
• Workflow YAML parsed successfully with Ruby Psych.
• git diff --check passed.

Deployment note

This PR does not deploy Cloud Run. The workflow guard prevents push-to-main deployment unless ENABLE_MAIN_PUSH_CLOUD_RUN_AUTOMATION is explicitly true.