fix(studio): preserve runtime network selection on update

[evanlowe]

Summary

• return the existing Runtime network configuration from the update capability endpoint
• hydrate the deployment draft with the current network mode, VPC, subnet, and shared internet settings
• keep Runtime update network controls read-only while displaying the correct selected state
• include rebuilt Studio static assets

Testing

• uv run pre-commit run --all-files
• uv run pytest tests/cli/test_studio_rbac.py -q (32 passed)
• npm test (405 passed)
• npm run build
• Browser E2E: open Agent detail, click Update, verify public + VPC, VPC ID, subnets, and shared internet access are preserved