refactor: DLO-16/17/18/20 — CLI simplification, config Pydantic, planner split, type system unification

DLO-16: Reduce cli.py from 1073 to 83 lines by registering Click commands from commands/*.py modules
DLO-17: Migrate Config to Pydantic BaseModel for validation
DLO-18: Split planner.py (826 lines) into orchestration, path rendering, and duplicate handling modules
DLO-20: Unify type system — convert 14 dataclasses to Pydantic BaseModel, keep TypedDicts as JSON schema hints

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/vlm/scanner.py

@@ -1,7 +1,7 @@
 """Inventory scanner for discovering and cataloging video files.
 
 This module implements the core scanning functionality for the Video Library Manager,
-including file discovery via `find`, metadata extraction, and categorization based on
+including file discovery, metadata extraction, and categorization based on
 directory structure.
 """
 
@@ -143,79 +143,7 @@ def scan_library(
 
 
 def _discover_video_paths(root: Path, video_extensions: list[str]) -> list[Path]:
-    """Discover matching video files under root.
-
-    Uses the system `find` command for traversal speed and falls back to Python
-    recursion if `find` is unavailable.
-    """
-    try:
-        return _discover_video_paths_with_find(root, video_extensions)
-    except FileNotFoundError:
-        logger.warning("`find` command not available - falling back to Python recursion")
-        return _discover_video_paths_recursive(root, video_extensions)
-
-
-def _log_find_nonzero_exit(returncode: int, stderr_text: str, discovered_count: int) -> None:
-    """Log the explicit contract for non-zero `find` exits.
-
-    Contract: if `find` emits partial stdout before failing, keep those paths and
-    continue with a warning. If no paths were emitted, return an empty result and
-    log that scan discovery was incomplete.
-    """
-    stderr_suffix = f": {stderr_text}" if stderr_text else ""
-    if discovered_count > 0:
-        logger.warning(
-            "find exited with code %s; using %s partial scan result(s)%s",
-            returncode,
-            discovered_count,
-            stderr_suffix,
-        )
-    else:
-        logger.warning(
-            "find exited with code %s and produced no scan results%s",
-            returncode,
-            stderr_suffix,
-        )
-
-
-def _discover_video_paths_with_find(root: Path, video_extensions: list[str]) -> list[Path]:
-    """Discover matching video files using the system `find` command."""
-    normalized_extensions = [ext.lower() for ext in video_extensions if ext]
-    if not normalized_extensions:
-        return []
-
-    command: list[str] = ["find", str(root), "-type", "f", "("]
-    for index, extension in enumerate(normalized_extensions):
-        if index > 0:
-            command.append("-o")
-        command.extend(["-iname", f"*{extension}"])
-    command.extend([")", "-print0"])
-
-    process = subprocess.Popen(
-        command,
-        stdout=subprocess.PIPE,
-        stderr=subprocess.PIPE
-    )
-    stdout, stderr = process.communicate()
-
-    discovered_paths: list[Path] = []
-    for path_bytes in stdout.split(b"\0"):
-        if not path_bytes:
-            continue
-        file_path = Path(os.fsdecode(path_bytes))
-        if _is_hidden_path(file_path, root):
-            continue
-        discovered_paths.append(file_path)
-
-    if process.returncode != 0:
-        stderr_text = stderr.decode(errors="replace").strip()
-        _log_find_nonzero_exit(process.returncode, stderr_text, len(discovered_paths))
-
-    return discovered_paths
-
-
-def _discover_video_paths_recursive(root: Path, video_extensions: list[str]) -> list[Path]:
-    """Fallback discovery using Python directory traversal."""
+    """Discover matching video files under root using os.scandir recursion."""
     discovered_paths: list[Path] = []
     for file_path in _scan_directory_recursive(root, video_extensions):
         if _is_hidden_path(file_path, root):