feat: add TemplateBuilderCompose SDK types and client method (#26350)

> [!NOTE]
> This PR was authored by Coder Agents on behalf of @jeremyruppel.

Part 3 of DEVEX-277 (POST /api/v2/templatebuilder/compose).

Adds SDK types and client method for the compose endpoint:

- `TemplateBuilderComposeRequest` with `BaseTemplateID` and `Modules` (list of `{ID, Variables}`). Registry URL is omitted from the request; it comes from server-side deployment config.
- `TemplateBuilderCompose(ctx, req)` client method that POSTs the request and returns raw `application/x-tar` bytes (matching the `Download` pattern in `codersdk/files.go`).
- Generated TypeScript types updated.

codersdk/templatebuilder.go

@@ -3,6 +3,7 @@ package codersdk
 import (
 	"context"
 	"encoding/json"
+	"io"
 	"net/http"
 	"net/url"
 )
@@ -95,3 +96,31 @@ func (c *Client) TemplateBuilderModules(ctx context.Context, base string) (Templ
 	var resp TemplateBuilderModulesResponse
 	return resp, json.NewDecoder(res.Body).Decode(&resp)
 }
+
+// TemplateBuilderComposeRequest is the request body for
+// POST /api/v2/templatebuilder/compose.
+type TemplateBuilderComposeRequest struct {
+	BaseTemplateID string                         `json:"base_template_id"`
+	Modules        []TemplateBuilderComposeModule `json:"modules"`
+}
+
+// TemplateBuilderComposeModule identifies a module and its variable
+// values for the compose request.
+type TemplateBuilderComposeModule struct {
+	ID        string            `json:"id"`
+	Variables map[string]string `json:"variables,omitempty"`
+}
+
+// TemplateBuilderCompose renders a base template with the selected
+// modules and returns the resulting tar archive bytes.
+func (c *Client) TemplateBuilderCompose(ctx context.Context, req TemplateBuilderComposeRequest) ([]byte, error) {
+	res, err := c.Request(ctx, http.MethodPost, "/api/v2/templatebuilder/compose", req)
+	if err != nil {
+		return nil, err
+	}
+	defer res.Body.Close()
+	if res.StatusCode != http.StatusOK {
+		return nil, ReadBodyAsError(res)
+	}
+	return io.ReadAll(res.Body)
+}

site/src/api/typesGenerated.ts

@@ -8172,6 +8172,26 @@ export interface TemplateBuilderBasesResponse {
 	readonly bases: readonly TemplateBuilderBase[];
 }
 
+// From codersdk/templatebuilder.go
+/**
+ * TemplateBuilderComposeModule identifies a module and its variable
+ * values for the compose request.
+ */
+export interface TemplateBuilderComposeModule {
+	readonly id: string;
+	readonly variables?: Record<string, string>;
+}
+
+// From codersdk/templatebuilder.go
+/**
+ * TemplateBuilderComposeRequest is the request body for
+ * POST /api/v2/templatebuilder/compose.
+ */
+export interface TemplateBuilderComposeRequest {
+	readonly base_template_id: string;
+	readonly modules: readonly TemplateBuilderComposeModule[];
+}
+
 // From codersdk/deployment.go
 export interface TemplateBuilderConfig {
 	readonly disabled?: boolean;