Migrate tests to Terraform for jetbrains, zed, and code-server (#307)

## Summary
- Introduces Terraform native tests (`terraform test`) alongside
existing Bun tests
- Migrates tests for modules: jetbrains, zed, and code-server
- Removes Bun test files for these migrated modules only
- Adds repo-wide test runner script for Terraform tests
- Updates docs and new-module sample to reflect Terraform tests

## Transition plan
- Mixed mode: Other modules retain Bun tests; CI should run both Bun and
Terraform tests temporarily
- Follow the linked epic to migrate remaining modules

## Test plan
- Run: `./scripts/terraform_test_all.sh` (passes locally)
- Bun tests still available for non-migrated modules

## Affected paths
- registry/coder/modules/jetbrains/jetbrains.tftest.hcl
- registry/coder/modules/zed/zed.tftest.hcl
- registry/coder/modules/code-server/code-server.tftest.hcl
- scripts/terraform_test_all.sh
- examples/modules/MODULE_NAME.tftest.hcl
- CONTRIBUTING.md


Contributes to #308

CONTRIBUTING.md

@@ -24,7 +24,7 @@ The Coder Registry is a collection of Terraform modules and templates for Coder
 
 ### Install Dependencies
 
-Install Bun:
+Install Bun (for formatting and scripts):
 
 ```bash
 curl -fsSL https://bun.sh/install | bash
@@ -124,19 +124,23 @@ This script generates:
    - Accurate description and usage examples
    - Correct icon path (usually `../../../../.icons/your-icon.svg`)
    - Proper tags that describe your module
-3. **Create `main.test.ts`** to test your module
+3. **Create at least one `.tftest.hcl`** to test your module with `terraform test`
 4. **Add any scripts** or additional files your module needs
 
 ### 4. Test and Submit
 
 ```bash
-# Test your module
-bun test -t 'module-name'
+# Test your module (from the module directory)
+terraform init -upgrade
+terraform test -verbose
+
+# Or run all tests in the repo
+./scripts/terraform_test_all.sh
 
 # Format code
-bun fmt
+bun run fmt
 
-# Commit and create PR
+# Commit and create PR (do not push to main directly)
 git add .
 git commit -m "Add [module-name] module"
 git push origin your-branch
@@ -335,11 +339,12 @@ coder templates push test-[template-name] -d .
 ### 2. Test Your Changes
 
 ```bash
-# Test a specific module
-bun test -t 'module-name'
+# Test a specific module (from the module directory)
+terraform init -upgrade
+terraform test -verbose
 
 # Test all modules
-bun test
+./scripts/terraform_test_all.sh
 ```
 
 ### 3. Maintain Backward Compatibility
@@ -388,7 +393,7 @@ Example: `https://github.com/coder/registry/compare/main...your-branch?template=
 ### Every Module Must Have
 
 - `main.tf` - Terraform code
-- `main.test.ts` - Working tests
+- One or more `.tftest.hcl` files - Working tests with `terraform test`
 - `README.md` - Documentation with frontmatter
 
 ### Every Template Must Have
@@ -488,6 +493,6 @@ When reporting bugs, include:
 2. **No tests** or broken tests
 3. **Hardcoded values** instead of variables
 4. **Breaking changes** without defaults
-5. **Not running** `bun fmt` before submitting
+5. **Not running** formatting (`bun run fmt`) and tests (`terraform test`) before submitting
 
 Happy contributing! 🚀