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_delete.go

@@ -0,0 +1,87 @@
+package cli
+
+import (
+	"fmt"
+	"strings"
+	"time"
+
+	"golang.org/x/xerrors"
+
+	"github.com/coder/pretty"
+
+	"github.com/coder/coder/v2/cli/cliui"
+	"github.com/coder/coder/v2/codersdk"
+	"github.com/coder/serpent"
+)
+
+func (r *RootCmd) taskDelete() *serpent.Command {
+	cmd := &serpent.Command{
+		Use:   "delete <task> [<task> ...]",
+		Short: "Delete tasks",
+		Long: FormatExamples(
+			Example{
+				Description: "Delete a single task.",
+				Command:     "$ coder task delete task1",
+			},
+			Example{
+				Description: "Delete multiple tasks.",
+				Command:     "$ coder task delete task1 task2 task3",
+			},
+			Example{
+				Description: "Delete a task without confirmation.",
+				Command:     "$ coder task delete task4 --yes",
+			},
+		),
+		Middleware: serpent.Chain(
+			serpent.RequireRangeArgs(1, -1),
+		),
+		Options: serpent.OptionSet{
+			cliui.SkipPromptOption(),
+		},
+		Handler: func(inv *serpent.Invocation) error {
+			ctx := inv.Context()
+			client, err := r.InitClient(inv)
+			if err != nil {
+				return err
+			}
+			exp := codersdk.NewExperimentalClient(client)
+
+			var tasks []codersdk.Task
+			for _, identifier := range inv.Args {
+				task, err := exp.TaskByIdentifier(ctx, identifier)
+				if err != nil {
+					return xerrors.Errorf("resolve task %q: %w", identifier, err)
+				}
+				tasks = append(tasks, task)
+			}
+
+			// Confirm deletion of the tasks.
+			var displayList []string
+			for _, task := range tasks {
+				displayList = append(displayList, fmt.Sprintf("%s/%s", task.OwnerName, task.Name))
+			}
+			_, err = cliui.Prompt(inv, cliui.PromptOptions{
+				Text:      fmt.Sprintf("Delete these tasks: %s?", pretty.Sprint(cliui.DefaultStyles.Code, strings.Join(displayList, ", "))),
+				IsConfirm: true,
+				Default:   cliui.ConfirmNo,
+			})
+			if err != nil {
+				return err
+			}
+
+			for i, task := range tasks {
+				display := displayList[i]
+				if err := exp.DeleteTask(ctx, task.OwnerName, task.ID); err != nil {
+					return xerrors.Errorf("delete task %q: %w", display, err)
+				}
+				_, _ = fmt.Fprintln(
+					inv.Stdout, "Deleted task "+pretty.Sprint(cliui.DefaultStyles.Keyword, display)+" at "+cliui.Timestamp(time.Now()),
+				)
+			}
+
+			return nil
+		},
+	}
+
+	return cmd
+}