feat(api): expose core and html primitives via top-level package exports

- Re-export Content and ContentType from omniread.core
- Re-export HTMLScraper and HTMLParser from omniread.html
- Define explicit __all__ for stable public API surface

omniread/__init__.py

@@ -0,0 +1,12 @@
+from .core import Content, ContentType
+from .html import HTMLScraper, HTMLParser
+
+__all__ = [
+    # core
+    "Content",
+    "ContentType",
+
+    # html
+    "HTMLScraper",
+    "HTMLParser",
+]

omniread/core/__init__.py

@@ -0,0 +1,6 @@
+from .content import Content, ContentType
+
+__all__ = [
+    "Content",
+    "ContentType",
+]

omniread/html/__init__.py

@@ -0,0 +1,7 @@
+from .scraper import HTMLScraper
+from .parser import HTMLParser
+
+__all__ = [
+    "HTMLScraper",
+    "HTMLParser",
+]