Epic: Migrate all modules from Bun tests to Terraform tests

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

- [x] Bootstrap Terraform test runner and docs
- [x] Migrate `coder/zed`
- [x] Migrate `coder/jetbrains`
- [x] 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.