feat: add TemplateBuilderCreateTemplate SDK types and client method - #26360

The TestEndpointsDocumented test derives expected IDs from summaries.
The @id 'compose-template-builder' did not match the kebab-cased
summary 'Compose template from base and modules'.

…talog

Reusable Go script that reads the Coder registry repo and generates
module.json and .tf.tmpl files for the template builder catalog. Parses
variable declarations from main.tf, frontmatter from README.md, and
pinned versions from git tags.

Usage:
  go run ./scripts/modulegen/ -registry /path/to/registry -output coderd/templatebuilder/modules

Handles escaped quotes and heredoc descriptions, skips variables with
heredoc defaults (cannot be represented in the builder UI), uses numeric
semver sorting for version tags, and exits non-zero on failures.

…t method

Add request/response types and client method for the new
POST /api/v2/templatebuilder/compose/template endpoint that will
compose a template and create it in a single request.

The request embeds compose parameters (base_template_id, modules)
alongside template creation parameters (organization_id, name,
display_name, description, icon, provisioner_tags).

Add ClassifyProvisionerError to detect known terraform init failure
modes (DNS resolution, connection refused, i/o timeout, TLS handshake
timeout) and return actionable user-facing messages. Unknown errors
pass through unchanged.

Add a synchronous endpoint that composes a template from a base and
modules, validates it via a provisioner import job, and creates the
template in a single request.

The handler: composes terraform files, bundles them as a tar archive,
inserts the file with hash-based dedup, creates a template version
with an import job, waits for the job to complete (2-minute timeout),
classifies any errors, then creates the template on success.

The waitForProvisionerJob helper uses an exponential backoff poll loop
with an onUpdate callback hook for future SSE streaming support.

Route: POST /api/v2/templatebuilder/compose/template

Apply canonical HCL formatting to rendered MainTF and ModulesTF
output using hclwrite.Format. This produces consistently formatted
terraform files regardless of template indentation.

The formatHCL helper returns input unchanged if it is empty.