feat: add TemplateBuilderCreateTemplate SDK types and client method (#26360)

Adds `POST /api/v2/templatebuilder/compose/template`, 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, inserts the
file with hash-based dedup, creates a template version with an import
job, waits up to 2 minutes for the job to complete, classifies errors
for known failure modes (network-unreachable registry, DNS failures),
then creates the template on success. Canceled and failed jobs return
appropriate error responses.

Also adds `hclwrite.Format` to composed terraform output for canonical
HCL formatting.

Closes https://linear.app/codercom/issue/DEVEX-279

<details>
<summary>Implementation notes</summary>

- SDK types and client method in `codersdk/templatebuilder.go` with
validation tags matching the standard template creation path
(`template_display_name`, `lt=128`)
- `ClassifyProvisionerError` in `coderd/templatebuilder/errors.go`
detects DNS, connection refused, i/o timeout, and TLS handshake failures
and returns actionable messages
- `waitForProvisionerJob` polls with a ramp-up interval schedule (100ms,
200ms, 500ms, then 1s steady) and accepts an `onUpdate` callback for
future SSE streaming
- Audit logging for both template and template version creation
- TOCTOU name uniqueness: early check for fast feedback, DB unique
constraint catch for the race window (returns 409, not 500)
- Swagger annotations for all error responses (400, 404, 409, 504)

</details>

> 🤖 Generated by Coder Agents

coderd/templatebuilder/compose.go

@@ -8,6 +8,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/hashicorp/hcl/v2/hclwrite"
 	"golang.org/x/xerrors"
 )
 
@@ -54,7 +55,7 @@ func Compose(req ComposeRequest) (*ComposeResult, error) {
 	}
 
 	if len(req.Modules) == 0 {
-		return &ComposeResult{MainTF: mainTF}, nil
+		return &ComposeResult{MainTF: formatHCL(mainTF)}, nil
 	}
 
 	agentName, err := ExtractAgentResourceName(mainTF)
@@ -78,11 +79,20 @@ func Compose(req ComposeRequest) (*ComposeResult, error) {
 	}
 
 	return &ComposeResult{
-		MainTF:    mainTF,
-		ModulesTF: modulesTF,
+		MainTF:    formatHCL(mainTF),
+		ModulesTF: formatHCL(modulesTF),
 	}, nil
 }
 
+// formatHCL applies canonical HCL formatting to src. If src is not valid
+// HCL the input is returned unchanged.
+func formatHCL(src []byte) []byte {
+	if len(src) == 0 {
+		return src
+	}
+	return hclwrite.Format(src)
+}
+
 // renderBase renders the base template for the given example ID.
 func renderBase(baseTemplateID string) ([]byte, error) {
 	renderCtx := DefaultBaseRenderContext(baseTemplateID)