Part of the Template Builder wizard PR stack.
## Backend fixes
1. **Registry URL scheme fix**: Default
`CODER_TEMPLATE_BUILDER_REGISTRY_URL` was `https://registry.coder.com`
but Terraform module registry addresses must be scheme-less. Changed to
`registry.coder.com`.
2. **Sensitive variable defaults**: Module `.tf.tmpl` files for
claude-code, aider, amazon-q had sensitive `variable` blocks without
`default`, causing `terraform plan` to fail during template import. Also
fixed the `templatebuildermodulegen` script.
3. **Auto-quote string variables**: The backend now accepts raw string
values from callers and wraps them in HCL quotes automatically.
Previously callers were required to send pre-quoted HCL literals, which
is not a reasonable API contract.
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> [!NOTE]
> Generated by Coder Agents on behalf of @jeremyruppel
Jeremy Ruppel
a30631198d