chore(package): migrate to src/ layout (#3920)

Migrates package structure to src/ layout following Python packaging
best practices.

All code moved from `llama_stack/` to `src/llama_stack/`. Public API
unchanged - imports remain `import llama_stack.*`.

Updated build configs, pre-commit hooks, scripts, and GitHub workflows
accordingly. All hooks pass, package builds cleanly.

**Developer note**: Reinstall after pulling: `pip install -e .`

src/llama_stack/cli/table.py

@@ -0,0 +1,39 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.
+
+from collections.abc import Iterable
+
+from rich.console import Console
+from rich.table import Table
+
+
+def print_table(rows, headers=None, separate_rows: bool = False, sort_by: Iterable[int] = tuple()):
+    # Convert rows and handle None values
+    rows = [[x or "" for x in row] for row in rows]
+
+    # Sort rows if sort_by is specified
+    if sort_by:
+        rows.sort(key=lambda x: tuple(x[i] for i in sort_by))
+
+    # Create Rich table
+    table = Table(show_lines=separate_rows)
+
+    # Add headers if provided
+    if headers:
+        for header in headers:
+            table.add_column(header, style="bold white")
+    else:
+        # Add unnamed columns based on first row
+        for _ in range(len(rows[0]) if rows else 0):
+            table.add_column()
+
+    # Add rows
+    for row in rows:
+        table.add_row(*row)
+
+    # Print table
+    console = Console()
+    console.print(table)