feat(cli): add enterprise external-workspaces CLI command (#19287)

This pull request introduces support for external workspace management, allowing users to register and manage workspaces that are provisioned and managed outside of the Coder.

* coder external-workspaces create - Creates a new external workspace (this command extends coder create)
  * Example: coder external-workspaces create ext-workspace --template=externally-managed-workspace -y
  * Checks if template has coder_external_agent resource before creating a workspace
* coder external-workspaces list - Lists all external workspaces
* coder external-workspaces agent-instructions <workspace name> <agent name> - Retrieves agent connection instruction
  * Example: coder external-workspaces agent-instructions ext-workspace main --output=json

docs/reference/cli/external-workspaces_list.md

@@ -0,0 +1,51 @@
+<!-- DO NOT EDIT | GENERATED CONTENT -->
+# external-workspaces list
+
+List external workspaces
+
+Aliases:
+
+* ls
+
+## Usage
+
+```console
+coder external-workspaces list [flags]
+```
+
+## Options
+
+### -a, --all
+
+|      |                   |
+|------|-------------------|
+| Type | <code>bool</code> |
+
+Specifies whether all workspaces will be listed or not.
+
+### --search
+
+|         |                       |
+|---------|-----------------------|
+| Type    | <code>string</code>   |
+| Default | <code>owner:me</code> |
+
+Search for a workspace with a query.
+
+### -c, --column
+
+|         |                                                                                                                                                                                                       |
+|---------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Type    | <code>[favorite\|workspace\|organization id\|organization name\|template\|status\|healthy\|last built\|current version\|outdated\|starts at\|starts next\|stops after\|stops next\|daily cost]</code> |
+| Default | <code>workspace,template,status,healthy,last built,current version,outdated</code>                                                                                                                    |
+
+Columns to display in table output.
+
+### -o, --output
+
+|         |                          |
+|---------|--------------------------|
+| Type    | <code>table\|json</code> |
+| Default | <code>table</code>       |
+
+Output format.