docs: expand devcontainer host vagrant architecture canvas

[2-Coatl]

Summary

• refresh the DevContainer Host with Vagrant canvas to emphasize running containers only inside the VM and add code examples
• document quality objectives, risks, and implementation checklist aligned to the Docker-less workstation constraint
• update the architecture index entry to reference the new canvas scope

Testing

• not run (documentation-only change)

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Codex Task

[chatgpt-codex-connector]

💡 Codex Review

https://github.com/2-Coatl/IACT---project/blob/bf2c6e761c1d262d8b7b92ccd1ac0c86d4dc813a/infrastructure/devcontainer/scripts/init_host.sh#L272-L276
Create devcontainer .env even when app env already exists

In setup_env_file the early return on lines 272‑276 exits as soon as api/callcentersite/env exists, so the new block that copies .devcontainer/.env.example to .devcontainer/.env never runs for existing checkouts. On an upgrade path (most developers already have api/callcentersite/env), the devcontainer compose now references .devcontainer/.env as a required env_file but the host script will not create it, causing docker compose to fail with “.env: no such file or directory” until users manually create it. The return should not short-circuit the devcontainer env creation.

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