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_send.md

@@ -0,0 +1,32 @@
+<!-- DO NOT EDIT | GENERATED CONTENT -->
+# task send
+
+Send input to a task
+
+## Usage
+
+```console
+coder task send [flags] <task> [<input> | --stdin]
+```
+
+## Description
+
+```console
+  - Send direct input to a task.:
+
+     $ coder task send task1 "Please also add unit tests"
+
+  - Send input from stdin to a task.:
+
+     $ echo "Please also add unit tests" | coder task send task1 --stdin
+```
+
+## Options
+
+### --stdin
+
+|      |                   |
+|------|-------------------|
+| Type | <code>bool</code> |
+
+Reads the input from stdin.