Refactor code style and improve documentation

- Standardized string quotes to single quotes across all files.
- Added docstrings to several functions and classes for better clarity.
- Updated mypy configuration in pyproject.toml for enhanced type checking.
- Ignored specific linting rules for test files in ruff configuration.
- Improved error messages in exception handling for better user feedback.
- Cleaned up code formatting and structure for consistency.

src/yt_shorts_downloader/models/__init__.py

@@ -3,4 +3,4 @@ from __future__ import annotations
 from .download import DownloadedVideo
 from .session import SessionCookie, SessionValidation
 
-__all__ = ["DownloadedVideo", "SessionCookie", "SessionValidation"]
+__all__ = ['DownloadedVideo', 'SessionCookie', 'SessionValidation']

src/yt_shorts_downloader/models/download.py

@@ -5,6 +5,8 @@ from dataclasses import dataclass
 
 @dataclass(frozen=True, slots=True)
 class DownloadedVideo:
+    """In-memory representation of a downloaded MP4 file."""
+
     filename: str
     content: bytes
-    media_type: str = "video/mp4"
+    media_type: str = 'video/mp4'

src/yt_shorts_downloader/models/session.py

@@ -5,6 +5,8 @@ from dataclasses import dataclass
 
 @dataclass(frozen=True, slots=True)
 class SessionCookie:
+    """Normalized cookie parsed from a Netscape session file."""
+
     domain: str
     include_subdomains: bool
     path: str
@@ -16,6 +18,8 @@ class SessionCookie:
 
 @dataclass(frozen=True, slots=True)
 class SessionValidation:
+    """Validation result for a candidate session cookie file."""
+
     exists: bool
     structurally_valid: bool
     fresh: bool