Epic: Migrate all modules from Bun tests to Terraform tests

[matifali]

This epic tracks migrating module tests from Bun-based tests to Terraform native testing (terraform test).

• Bootstrap Terraform test runner and docs
• Migrate coder/zed
• Migrate coder/jetbrains
• Migrate coder/code-server
• Migrate coder/agentapi
• Migrate coder/devcontainers-cli
• Migrate coder/kiro
• Migrate coder/jetbrains-fleet
• Migrate coder/jetbrains-gateway
• Migrate coder/vscode-web
• Migrate coder/vscode-desktop
• Migrate coder/vault-token
• Migrate coder/vault-jwt
• Migrate coder/vault-github
• Migrate coder/slackme
• Migrate coder/personalize
• Migrate coder/kasmvnc
• Migrate coder/jupyterlab
• Migrate coder/jfrog-token
• Migrate coder/jfrog-oauth
• Migrate coder/github-upload-public-key
• Migrate coder/git-config
• Migrate coder/git-clone
• Migrate coder/gcp-region
• Migrate coder/fly-region
• Migrate coder/dotfiles
• Migrate coder/cursor
• Migrate coder/coder-login
• Migrate coder/azure-region
• Migrate coder/aws-region
• Migrate anomaly/tmux
• Migrate coder-labs/gemini
• Migrate whizus/exoscale-instance-type
• Migrate whizus/exoscale-zone
• Migrate thezoker/nodejs

Notes

• Remove corresponding main.test.ts when a module gets migrated.
• Prefer plan runs for structural assertions; use apply only when outputs are required.
• Keep Bun harness until all modules are migrated, then remove Bun deps and tooling.