lib.version: Add API docstrings

The lib.version module carries no documentation: the Syntax, Component and
Boundary types, the Version and Dependency classes and their public methods
are bare, and the compatibility tiers the next_* stepping methods implement
are not documented anywhere.

Add docstrings: a line each for the base.py types, the compatibility
tier table in the Version class, and a short description for every
public method, with the three next_* methods citing the tier each one
steps to.

Assisted-by: unsloth/Qwen3.8-27B-GGUF:Q4_K_M with pi.dev v0.84.2
Signed-off-by: Jan Lindemann <jan@janware.com>

src/python/jw/pkg/lib/version/base.py

@@ -8,11 +8,15 @@ if TYPE_CHECKING:
     from .Version import Version
 
 class Syntax(Enum):  # export
+    """Syntaxes for rendered version constraints"""
+
     DEBIAN = auto()
     SEM_VER = auto()
     NAMES_ONLY = auto()
 
 class Component(Flag):  # export
+    """Version components that parts_str() can extract"""
+
     ID = auto()
     MAJOR = auto()
     MINOR = auto()
@@ -21,6 +25,8 @@ class Component(Flag):  # export
     CORE = MAJOR | MINOR | MICRO
 
 class Boundary(NamedTuple):  # export
+    """A comparison operator and the Version it bounds"""
+
     op: str
     version: Version