Initial commit: doujinshi-dl generic plugin framework

History reset as part of DMCA compliance. The project has been
refactored into a generic, site-agnostic download framework.
Site-specific logic lives in separate plugin packages.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

doujinshi_dl/core/registry.py

@@ -0,0 +1,28 @@
+# coding: utf-8
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from doujinshi_dl.core.plugin import BasePlugin
+
+
+def get_plugin(name: str) -> 'BasePlugin':
+    from importlib.metadata import entry_points
+    eps = entry_points(group='doujinshi_dl.plugins')
+    for ep in eps:
+        if ep.name == name:
+            return ep.load()
+    raise KeyError(
+        f"Plugin {name!r} not found. "
+        f"Install it with: pip install doujinshi-dl-{name}"
+    )
+
+
+def get_first_plugin() -> 'BasePlugin':
+    from importlib.metadata import entry_points
+    eps = list(entry_points(group='doujinshi_dl.plugins'))
+    if not eps:
+        raise RuntimeError(
+            "No doujinshi-dl plugin installed. "
+            "Install a plugin from PyPI, e.g.: pip install doujinshi-dl-<name>"
+        )
+    return eps[0].load()