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 🏄🏻‍♂️

docs/reference/cli/task.md

@@ -0,0 +1,25 @@
+<!-- DO NOT EDIT | GENERATED CONTENT -->
+# task
+
+Manage tasks
+
+Aliases:
+
+* tasks
+
+## Usage
+
+```console
+coder task
+```
+
+## Subcommands
+
+| Name                                    | Purpose                    |
+|-----------------------------------------|----------------------------|
+| [<code>create</code>](./task_create.md) | Create a task              |
+| [<code>delete</code>](./task_delete.md) | Delete tasks               |
+| [<code>list</code>](./task_list.md)     | List tasks                 |
+| [<code>logs</code>](./task_logs.md)     | Show a task's logs         |
+| [<code>send</code>](./task_send.md)     | Send input to a task       |
+| [<code>status</code>](./task_status.md) | Show the status of a task. |