feat(cli): add 'coder login token' command to print session token (#21627)

Adds a new subcommand to print the current session token for use in
scripts and automation, similar to `gh auth token`.

## Usage

```bash
CODER_SESSION_TOKEN=$(coder login token)
```

Fixes #21515

docs/reference/cli/login.md

@@ -15,6 +15,12 @@ coder login [flags] [<url>]
 By default, the session token is stored in the operating system keyring on macOS and Windows and a plain text file on Linux. Use the --use-keyring flag or CODER_USE_KEYRING environment variable to change the storage mechanism.
 ```
 
+## Subcommands
+
+| Name                                   | Purpose                         |
+|----------------------------------------|---------------------------------|
+| [<code>token</code>](./login_token.md) | Print the current session token |
+
 ## Options
 
 ### --first-user-email

docs/reference/cli/login_token.md

@@ -0,0 +1,16 @@
+<!-- DO NOT EDIT | GENERATED CONTENT -->
+# login token
+
+Print the current session token
+
+## Usage
+
+```console
+coder login token
+```
+
+## Description
+
+```console
+Print the session token for use in scripts and automation.
+```