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/tests/unit_tests/test_util.py

@@ -1,6 +1,11 @@
 from unittest.mock import patch
 
-from langgraph_cli.util import clean_empty_lines, warn_non_wolfi_distro
+from langgraph_cli.util import (
+    _extract_deployment_url,
+    clean_empty_lines,
+    format_deployments_table,
+    warn_non_wolfi_distro,
+)
 
 
 def test_clean_empty_lines():
@@ -186,3 +191,36 @@ def test_warn_non_wolfi_distro_does_not_modify_config():
     warn_non_wolfi_distro(config_copy)
 
     assert config_copy == original_config  # Config should remain unchanged
+
+
+def test_extract_deployment_url_uses_custom_url():
+    deployment = {"source_config": {"custom_url": "https://example.com/custom"}}
+    assert _extract_deployment_url(deployment) == "https://example.com/custom"
+
+
+def test_extract_deployment_url_defaults_to_dash():
+    assert _extract_deployment_url({"id": "dep-123"}) == "-"
+
+
+def test_format_deployments_table():
+    output = format_deployments_table(
+        [
+            {
+                "id": "dep-123",
+                "name": "alpha",
+                "source_config": {"custom_url": "https://alpha.example.com"},
+            },
+            {
+                "id": "dep-456",
+                "name": "beta",
+                "url": "https://beta.example.com",
+            },
+        ]
+    )
+    assert "Deployment ID" in output
+    assert "Deployment Name" in output
+    assert "Deployment URL" in output
+    assert "dep-123" in output
+    assert "alpha" in output
+    assert "https://alpha.example.com" in output
+    assert "dep-456" in output