feat: add MCP tools for ChatGPT (#19102)

Addresses https://github.com/coder/internal/issues/772.

Adds the toolset query parameter to the `/api/experimental/mcp/http` endpoint, which, when set to "chatgpt", exposes new `fetch` and `search` tools compatible with ChatGPT, as described in the
[ChatGPT docs](https://platform.openai.com/docs/mcp). These tools are
exposed in isolation because in my usage I found that ChatGPT refuses to
connect to Coder if it sees additional MCP tools.

<img width="1248" height="908" alt="Screenshot 2025-07-30 at 16 36 56"
src="https://github.com/user-attachments/assets/ca31e57b-d18b-4998-9554-7a96a141527a"
/>

codersdk/toolsdk/toolsdk.go

@@ -36,6 +36,8 @@ const (
 	ToolNameCreateTemplate              = "coder_create_template"
 	ToolNameDeleteTemplate              = "coder_delete_template"
 	ToolNameWorkspaceBash               = "coder_workspace_bash"
+	ToolNameChatGPTSearch               = "search"
+	ToolNameChatGPTFetch                = "fetch"
 )
 
 func NewDeps(client *codersdk.Client, opts ...func(*Deps)) (Deps, error) {
@@ -56,6 +58,13 @@ type Deps struct {
 	report      func(ReportTaskArgs) error
 }
 
+func (d Deps) ServerURL() string {
+	serverURLCopy := *d.coderClient.URL
+	serverURLCopy.Path = ""
+	serverURLCopy.RawQuery = ""
+	return serverURLCopy.String()
+}
+
 func WithTaskReporter(fn func(ReportTaskArgs) error) func(*Deps) {
 	return func(d *Deps) {
 		d.report = fn
@@ -194,6 +203,8 @@ var All = []GenericTool{
 	UploadTarFile.Generic(),
 	UpdateTemplateActiveVersion.Generic(),
 	WorkspaceBash.Generic(),
+	ChatGPTSearch.Generic(),
+	ChatGPTFetch.Generic(),
 }
 
 type ReportTaskArgs struct {