feat(cli): promote tasks commands from experimental to GA (#20916)

## Overview

This change promotes the tasks CLI commands from `coder exp task` to
`coder task`, marking them as generally available (GA).

## Migration

Users will need to update their scripts from:

```shell
coder exp task create "my task"
```

To:
```shell
coder task create "my task"
```

---

🤖 This change was written by Claude Sonnet 4.5 Thinking using [mux](https://github.com/coder/mux) and reviewed by a human 🏄🏻‍♂️

cli/task_send_test.go

@@ -0,0 +1,171 @@
+package cli_test
+
+import (
+	"encoding/json"
+	"net/http"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	agentapisdk "github.com/coder/agentapi-sdk-go"
+
+	"github.com/coder/coder/v2/cli/clitest"
+	"github.com/coder/coder/v2/coderd/coderdtest"
+	"github.com/coder/coder/v2/coderd/httpapi"
+	"github.com/coder/coder/v2/testutil"
+)
+
+func Test_TaskSend(t *testing.T) {
+	t.Parallel()
+
+	t.Run("ByTaskName_WithArgument", func(t *testing.T) {
+		t.Parallel()
+		ctx := testutil.Context(t, testutil.WaitLong)
+
+		client, task := setupCLITaskTest(ctx, t, fakeAgentAPITaskSendOK(t, "carry on with the task", "you got it"))
+		userClient := client
+
+		var stdout strings.Builder
+		inv, root := clitest.New(t, "task", "send", task.Name, "carry on with the task")
+		inv.Stdout = &stdout
+		clitest.SetupConfig(t, userClient, root)
+
+		err := inv.WithContext(ctx).Run()
+		require.NoError(t, err)
+	})
+
+	t.Run("ByTaskID_WithArgument", func(t *testing.T) {
+		t.Parallel()
+		ctx := testutil.Context(t, testutil.WaitLong)
+
+		client, task := setupCLITaskTest(ctx, t, fakeAgentAPITaskSendOK(t, "carry on with the task", "you got it"))
+		userClient := client
+
+		var stdout strings.Builder
+		inv, root := clitest.New(t, "task", "send", task.ID.String(), "carry on with the task")
+		inv.Stdout = &stdout
+		clitest.SetupConfig(t, userClient, root)
+
+		err := inv.WithContext(ctx).Run()
+		require.NoError(t, err)
+	})
+
+	t.Run("ByTaskName_WithStdin", func(t *testing.T) {
+		t.Parallel()
+		ctx := testutil.Context(t, testutil.WaitLong)
+
+		client, task := setupCLITaskTest(ctx, t, fakeAgentAPITaskSendOK(t, "carry on with the task", "you got it"))
+		userClient := client
+
+		var stdout strings.Builder
+		inv, root := clitest.New(t, "task", "send", task.Name, "--stdin")
+		inv.Stdout = &stdout
+		inv.Stdin = strings.NewReader("carry on with the task")
+		clitest.SetupConfig(t, userClient, root)
+
+		err := inv.WithContext(ctx).Run()
+		require.NoError(t, err)
+	})
+
+	t.Run("TaskNotFound_ByName", func(t *testing.T) {
+		t.Parallel()
+		ctx := testutil.Context(t, testutil.WaitLong)
+
+		client := coderdtest.New(t, &coderdtest.Options{IncludeProvisionerDaemon: true})
+		owner := coderdtest.CreateFirstUser(t, client)
+		userClient, _ := coderdtest.CreateAnotherUser(t, client, owner.OrganizationID)
+
+		var stdout strings.Builder
+		inv, root := clitest.New(t, "task", "send", "doesnotexist", "some task input")
+		inv.Stdout = &stdout
+		clitest.SetupConfig(t, userClient, root)
+
+		err := inv.WithContext(ctx).Run()
+		require.Error(t, err)
+		require.ErrorContains(t, err, httpapi.ResourceNotFoundResponse.Message)
+	})
+
+	t.Run("TaskNotFound_ByID", func(t *testing.T) {
+		t.Parallel()
+		ctx := testutil.Context(t, testutil.WaitLong)
+
+		client := coderdtest.New(t, &coderdtest.Options{IncludeProvisionerDaemon: true})
+		owner := coderdtest.CreateFirstUser(t, client)
+		userClient, _ := coderdtest.CreateAnotherUser(t, client, owner.OrganizationID)
+
+		var stdout strings.Builder
+		inv, root := clitest.New(t, "task", "send", uuid.Nil.String(), "some task input")
+		inv.Stdout = &stdout
+		clitest.SetupConfig(t, userClient, root)
+
+		err := inv.WithContext(ctx).Run()
+		require.Error(t, err)
+		require.ErrorContains(t, err, httpapi.ResourceNotFoundResponse.Message)
+	})
+
+	t.Run("SendError", func(t *testing.T) {
+		t.Parallel()
+		ctx := testutil.Context(t, testutil.WaitLong)
+
+		userClient, task := setupCLITaskTest(ctx, t, fakeAgentAPITaskSendErr(t, assert.AnError))
+
+		var stdout strings.Builder
+		inv, root := clitest.New(t, "task", "send", task.Name, "some task input")
+		inv.Stdout = &stdout
+		clitest.SetupConfig(t, userClient, root)
+
+		err := inv.WithContext(ctx).Run()
+		require.ErrorContains(t, err, assert.AnError.Error())
+	})
+}
+
+func fakeAgentAPITaskSendOK(t *testing.T, expectMessage, returnMessage string) map[string]http.HandlerFunc {
+	return map[string]http.HandlerFunc{
+		"/status": func(w http.ResponseWriter, r *http.Request) {
+			w.Header().Set("Content-Type", "application/json")
+			_ = json.NewEncoder(w).Encode(map[string]string{
+				"status": "stable",
+			})
+		},
+		"/message": func(w http.ResponseWriter, r *http.Request) {
+			w.Header().Set("Content-Type", "application/json")
+			w.WriteHeader(http.StatusOK)
+			var msg agentapisdk.PostMessageParams
+			if err := json.NewDecoder(r.Body).Decode(&msg); err != nil {
+				http.Error(w, err.Error(), http.StatusBadRequest)
+				return
+			}
+			assert.Equal(t, expectMessage, msg.Content)
+			message := agentapisdk.Message{
+				Id:      999,
+				Role:    agentapisdk.RoleAgent,
+				Content: returnMessage,
+				Time:    time.Now(),
+			}
+			_ = json.NewEncoder(w).Encode(message)
+		},
+	}
+}
+
+func fakeAgentAPITaskSendErr(t *testing.T, returnErr error) map[string]http.HandlerFunc {
+	return map[string]http.HandlerFunc{
+		"/status": func(w http.ResponseWriter, r *http.Request) {
+			w.Header().Set("Content-Type", "application/json")
+			_ = json.NewEncoder(w).Encode(map[string]string{
+				"status": "stable",
+			})
+		},
+		"/message": func(w http.ResponseWriter, r *http.Request) {
+			if r.Method != http.MethodPost {
+				http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
+				return
+			}
+			w.WriteHeader(http.StatusInternalServerError)
+			_, _ = w.Write([]byte(returnErr.Error()))
+		},
+	}
+}