feat(cli): Add deploy list and deploy delete subcommands (#7106)

### Summary
This PR introduces a subcommand implementation that allows `langgraph
deploy list` and `langgraph deploy delete` subcommands.

#### `langgraph deploy list`
```bash
(env) andrewnguonly@Andrew-Nguonly-KC23X90J02 langgraph % langgraph deploy list --help                                                                              ⎈ gke_langchain-test-387119_us-west1_langgraph-cloud-us-west1
Usage: langgraph deploy list [OPTIONS]

  [Beta] List LangSmith Deployments.

Options:
  --name-contains TEXT  Only show deployments whose names contain this value.
  --api-key TEXT        API key. Can also be set via LANGGRAPH_HOST_API_KEY,
                        LANGSMITH_API_KEY, or LANGCHAIN_API_KEY environment
                        variable or .env file.
  --help                Show this message and exit.
```

Output example:
```bash
(env) andrewnguonly@Andrew-Nguonly-KC23X90J02 cli % langgraph deploy list
Deployment ID                         Deployment Name             Deployment URL                                                                      
------------------------------------  --------------------------  ------------------------------------------------------------------------------------
a40d6567-87c0-485a-a23d-94309a7d4519  ht-andrew-test-04           -                                                                                   
9da26acb-d0c9-4af0-af9e-f3fe8dfe85bc  ht-anirudh-deployment-test  https://ht-anirudh-deployment-test-428af4737f8a533cb2b107587eb8f38f.us.langgraph.app
```

#### `langgraph deploy delete`
```bash
(env) andrewnguonly@Andrew-Nguonly-KC23X90J02 langgraph % langgraph deploy delete --help                                                                            ⎈ gke_langchain-test-387119_us-west1_langgraph-cloud-us-west1
Usage: langgraph deploy delete [OPTIONS] DEPLOYMENT_ID

  [Beta] Delete a LangSmith Deployment.

Options:
  --force         Delete without prompting for confirmation.
  --api-key TEXT  API key. Can also be set via LANGGRAPH_HOST_API_KEY,
                  LANGSMITH_API_KEY, or LANGCHAIN_API_KEY environment variable
                  or .env file.
  --help          Show this message and exit.
```

Output example:
```bash
(env) andrewnguonly@Andrew-Nguonly-KC23X90J02 cli % langgraph deploy delete a40d6567-87c0-485a-a23d-94309a7d4519
Are you sure you want to delete deployment ID a40d6567-87c0-485a-a23d-94309a7d4519? (Y/n): Y
Host API key: 
Deleted deployment a40d6567-87c0-485a-a23d-94309a7d4519.
```

```bash
(env) andrewnguonly@Andrew-Nguonly-KC23X90J02 cli % langgraph deploy delete a40d6567-87c0-485a-a23d-94309a7d4519
Are you sure you want to delete deployment ID a40d6567-87c0-485a-a23d-94309a7d4519? (Y/n): n
Aborted!
```

```bash
(env) andrewnguonly@Andrew-Nguonly-KC23X90J02 cli % langgraph deploy delete 9da26acb-d0c9-4af0-af9e-f3fe8dfe85bc --force
Host API key: 
Deleted deployment 9da26acb-d0c9-4af0-af9e-f3fe8dfe85bc.
```

libs/cli/langgraph_cli/util.py

@@ -1,3 +1,5 @@
+from collections.abc import Sequence
+
 import click
 
 
@@ -23,3 +25,35 @@ def warn_non_wolfi_distro(config_json: dict) -> None:
             fg="yellow",
         )
         click.secho("")  # Empty line for better readability
+
+
+def _extract_deployment_url(deployment: dict[str, object]) -> str:
+    source_config = deployment.get("source_config")
+    if isinstance(source_config, dict):
+        custom_url = source_config.get("custom_url")
+        if isinstance(custom_url, str) and custom_url:
+            return custom_url
+    return "-"
+
+
+def format_deployments_table(deployments: Sequence[dict[str, object]]) -> str:
+    headers = ("Deployment ID", "Deployment Name", "Deployment URL")
+    rows = [
+        (
+            str(deployment.get("id", "-") or "-"),
+            str(deployment.get("name", "-") or "-"),
+            _extract_deployment_url(deployment),
+        )
+        for deployment in deployments
+    ]
+    widths = [
+        max(len(headers[index]), *(len(row[index]) for row in rows))
+        for index in range(len(headers))
+    ]
+
+    def format_row(row: Sequence[str]) -> str:
+        return "  ".join(value.ljust(widths[index]) for index, value in enumerate(row))
+
+    lines = [format_row(headers), format_row(tuple("-" * width for width in widths))]
+    lines.extend(format_row(row) for row in rows)
+    return "\n".join(lines)