refactor: derive __version__ from package metadata (single source)

Signed-off-by: disqualifier <dev@disqualifier.me>

src/dpy_commons/__init__.py

@@ -4,6 +4,8 @@ a module of functions grouped by concern: message/embed parsing, embed sanitizin
 limit-fitting, link extraction, text chunking, timestamp helpers, interactive await-prompts,
 and a limit-safe send. see each submodule's docstring for the contract.
 """
+from importlib.metadata import PackageNotFoundError, version
+
 from .embeds import fit_embed, sanitize_embed, split_embeds
 from .limits import (
     EMBED_AUTHOR,
@@ -29,7 +31,10 @@ from .text import (
     wrap_bare_links,
 )
 
-__version__ = "0.1.2"
+try:
+    __version__ = version("dpy_commons")
+except PackageNotFoundError:
+    __version__ = "0.0.0+unknown"
 
 __all__ = [
     "parse_message",