Humanize CLI command group descriptions a bit (#137)

# What does this PR do?

Descriptions were repetitive and verbose, some were truncated by click
rendering (trailing ... ellipsis). This is an attempt to simplify /
shorten / clarify the descriptions.

[//]: # (If resolving an issue, uncomment and update the line below)
[//]: # (Closes #[issue-number])

## Test Plan

Before:

```
 llama-stack-client --help
Usage: llama-stack-client [OPTIONS] COMMAND [ARGS]...

  Welcome to the LlamaStackClient CLI

Options:
  --version        Show the version and exit.
  --endpoint TEXT  Llama Stack distribution endpoint
  --api-key TEXT   Llama Stack distribution API key
  --config TEXT    Path to config file
  --help           Show this message and exit.

Commands:
  configure          Configure Llama Stack Client CLI
  datasets           Query details about available datasets on Llama...
  eval               Run evaluation tasks
  eval_tasks         Query details about available eval tasks type on...
  inference          Query details about available inference endpoints on...
  inspect            Query details about available versions on Llama...
  models             Query details about available models on Llama Stack...
  post_training      Query details about available post_training...
  providers          Query details about available providers on Llama...
  scoring_functions  Manage scoring functions
  shields            Query details about available safety shields on...
  toolgroups         Query details about available toolgroups on Llama...
  vector_dbs         Query details about available vector dbs on...
```

After:

```
 llama-stack-client --help
Usage: llama-stack-client [OPTIONS] COMMAND [ARGS]...

  Welcome to the LlamaStackClient CLI

Options:
  --version        Show the version and exit.
  --endpoint TEXT  Llama Stack distribution endpoint
  --api-key TEXT   Llama Stack distribution API key
  --config TEXT    Path to config file
  --help           Show this message and exit.

Commands:
  configure          Configure Llama Stack Client CLI.
  datasets           Manage datasets.
  eval               Run evaluation tasks.
  eval_tasks         Manage evaluation tasks.
  inference          Inference (chat).
  inspect            Inspect server configuration.
  models             Manage GenAI models.
  post_training      Post-training.
  providers          Manage API providers.
  scoring_functions  Manage scoring functions.
  shields            Manage safety shield services.
  toolgroups         Manage available tool groups.
  vector_dbs         Manage vector databases.
```

[//]: # (## Documentation)
[//]: # (- [ ] Added a Changelog entry if the change is significant)

Signed-off-by: Ihar Hrachyshka <ihar.hrachyshka@gmail.com>

Author: Ihar Hrachyshka

src/llama_stack_client/lib/cli/configure.py

@@ -26,7 +26,7 @@ def get_config():
 @click.option("--endpoint", type=str, help="Llama Stack distribution endpoint", default="")
 @click.option("--api-key", type=str, help="Llama Stack distribution API key", default="")
 def configure(endpoint: str | None, api_key: str | None):
-    """Configure Llama Stack Client CLI"""
+    """Configure Llama Stack Client CLI."""
     os.makedirs(LLAMA_STACK_CLIENT_CONFIG_DIR, exist_ok=True)
     config_path = get_config_file_path()
 

src/llama_stack_client/lib/cli/datasets/datasets.py

@@ -11,8 +11,7 @@
 
 @click.group()
 def datasets():
-    """Query details about available datasets on Llama Stack distribution."""
-    pass
+    """Manage datasets."""
 
 
 # Register subcommands

src/llama_stack_client/lib/cli/eval/eval.py

@@ -13,8 +13,7 @@
 
 @click.group()
 def eval():
-    """Run evaluation tasks"""
-    pass
+    """Run evaluation tasks."""
 
 
 # Register subcommands

src/llama_stack_client/lib/cli/eval_tasks/eval_tasks.py

@@ -17,8 +17,7 @@
 
 @click.group()
 def eval_tasks():
-    """Query details about available eval tasks type on distribution."""
-    pass
+    """Manage evaluation tasks."""
 
 
 @eval_tasks.command()

src/llama_stack_client/lib/cli/inference/inference.py

@@ -15,8 +15,7 @@
 
 @click.group()
 def inference():
-    """Query details about available inference endpoints on distribution."""
-    pass
+    """Inference (chat)."""
 
 
 @click.command("chat-completion")

src/llama_stack_client/lib/cli/inspect/inspect.py

@@ -5,8 +5,7 @@
 
 @click.group()
 def inspect():
-    """Query details about available versions on Llama Stack distribution."""
-    pass
+    """Inspect server configuration."""
 
 
 # Register subcommands

src/llama_stack_client/lib/cli/models/models.py

@@ -15,8 +15,7 @@
 
 @click.group()
 def models():
-    """Query details about available models on Llama Stack distribution."""
-    pass
+    """Manage GenAI models."""
 
 
 @click.command(name="list", help="Show available llama models at distribution endpoint")

src/llama_stack_client/lib/cli/post_training/post_training.py

@@ -16,8 +16,7 @@
 
 @click.group()
 def post_training():
-    """Query details about available post_training endpoints on distribution."""
-    pass
+    """Post-training."""
 
 
 @click.command("supervised_fine_tune")

src/llama_stack_client/lib/cli/providers/providers.py

@@ -5,8 +5,7 @@
 
 @click.group()
 def providers():
-    """Query details about available providers on Llama Stack distribution."""
-    pass
+    """Manage API providers."""
 
 
 # Register subcommands

src/llama_stack_client/lib/cli/scoring_functions/scoring_functions.py

@@ -15,8 +15,7 @@
 
 @click.group()
 def scoring_functions():
-    """Manage scoring functions"""
-    pass
+    """Manage scoring functions."""
 
 
 @scoring_functions.command()