Add build metadata to Valet UI

[yourbuddyconner]

Summary

• Add deploy-time client build metadata for environment, commit hash, and production version tag
• Surface the metadata in the app header and session chat header with distinct dev/prod chrome
• Pass full Git history to the prod deploy job so exact tag lookup works during release builds

Validation

• pnpm --filter @valet/client typecheck
• bash -n scripts/deploy.sh
• ruby -e 'require "yaml"; YAML.load_file(".github/workflows/deploy-prod.yml")'
• git diff --check
• production client build with sample VITE_BUILD_COMMIT_HASH and VITE_BUILD_VERSION_TAG