Simplify package configuration and document behavioral differences

- Removed redundant package-data configuration, relying on MANIFEST.in
- Added documentation about behavioral differences between package and source installation
- Clarified that include-package-data=true uses MANIFEST.in for data files

Co-authored-by: RockChinQ <45992437+RockChinQ@users.noreply.github.com>

pyproject.toml

@@ -111,13 +111,6 @@ build-backend = "setuptools.build_meta"
 packages = { find = {} }
 include-package-data = true
 
-[tool.setuptools.package-data]
-langbot = [
-    "web/out/**/*",
-    "templates/**/*",
-    "res/**/*",
-]
-
 [dependency-groups]
 dev = [
     "pre-commit>=4.2.0",