fix: Escape Click’s Wrapping in bulled lists of adk web options

Merge #4338

### Link to Issue or Description of Change

**2. Or, if no issue exists, describe the change:**

**Problem:**
Click collapses intended bullet lists in the service URI options.

<img width="709" height="267" alt="image" src="https://github.com/user-attachments/assets/5f74d8a6-f343-41a4-ba6d-570ed0076932" />

**Solution:**
Add `\b` on a line by itself before the formatted block to preserve blank lines.

### Testing Plan

This is format improvement of help message, so I think there is no need to add test case.

**Unit Tests:**

- [ ] I have added or updated unit tests for my change.
- [x] All unit tests pass locally.

```
% pytest tests/unittests/cli  # Python 3.13.8
===================================== 260 passed, 140 warnings in 9.30s ======================================
```

**Manual End-to-End (E2E) Tests:**

`adk web --help`

```
  --session_service_uri TEXT      Optional. The URI of the session service. If set, ADK uses this service.

                                  If unset, ADK chooses a default session service (see
                                  --use_local_storage).
                                  - Use 'agentengine://<agent_engine>' to connect to Agent Engine
                                    sessions. <agent_engine> can either be the full qualified resource
                                    name 'projects/abc/locations/us-central1/reasoningEngines/123' or
                                    the resource id '123'.
                                  - Use 'memory://' to run with the in-memory session service.
                                  - Use 'sqlite://<path_to_sqlite_file>' to connect to a SQLite DB.
                                  - See https://docs.sqlalchemy.org/en/20/core/engines.html#backend-specific-urls
                                    for supported database URIs.
```

### Checklist

- [x] I have read the [CONTRIBUTING.md](https://github.com/google/adk-python/blob/main/CONTRIBUTING.md) document.
- [x] I have performed a self-review of my own code.
- [x] I have commented my code, particularly in hard-to-understand areas.
- [x] I have added tests that prove my fix is effective or that my feature works.
- [x] New and existing unit tests pass locally with my changes.
- [x] I have manually tested my changes end-to-end.
- [x] Any dependent changes have been merged and published in downstream modules.

COPYBARA_INTEGRATE_REVIEW=#4338 from ftnext:escape-wrapping-web-options-bullet-list 9466731
PiperOrigin-RevId: 865533252

Author: ftnext

src/google/adk/cli/cli_tools_click.py

@@ -459,6 +459,7 @@ def decorator(func):
             Optional. The URI of the session service.
             If set, ADK uses this service.
 
+            \b
             If unset, ADK chooses a default session service (see
             --use_local_storage).
             - Use 'agentengine://<agent_engine>' to connect to Agent Engine
@@ -478,6 +479,7 @@ def decorator(func):
             Optional. The URI of the artifact service.
             If set, ADK uses this service.
 
+            \b
             If unset, ADK chooses a default artifact service (see
             --use_local_storage).
             - Use 'gs://<bucket_name>' to connect to the GCS artifact service.
@@ -503,6 +505,7 @@ def decorator(func):
         "--memory_service_uri",
         type=str,
         help=textwrap.dedent("""\
+            \b
             Optional. The URI of the memory service.
             - Use 'rag://<rag_corpus_id>' to connect to Vertex AI Rag Memory Service.
             - Use 'agentengine://<agent_engine>' to connect to Agent Engine