build(deps): bump pageindex 0.3.0.dev2 -> 0.3.0.dev3

Vetted: identical Requires-Dist/Requires-Python to dev2; IndexConfig,
PageIndexClient, and IndexConfig.max_concurrency (used by #174) all still
present; wheel/sdist hashes verified against PyPI. uv.lock regenerated via
`uv lock` (change scoped to the pageindex entry). Also aligns the stale
dev1 reference in the config README.

Author: KylinMountain

examples/configuration/README.md

@@ -12,7 +12,7 @@ pip install openkb
 ```
 
 OpenKB pins a **pre-release** of its PageIndex dependency
-(`pageindex==0.3.0.dev1`), which some installers skip by default. If an install
+(`pageindex==0.3.0.dev3`), which some installers skip by default. If an install
 can't resolve `pageindex`, allow pre-releases:
 
 ```bash

pyproject.toml

@@ -32,7 +32,7 @@ keywords = ["ai", "rag", "retrieval", "knowledge-base", "llm", "pageindex", "age
 # returning empty Responses output (BerriAI/litellm#25429) and
 # auto-injects GitHub Copilot IDE-auth headers.
 dependencies = [
-    "pageindex==0.3.0.dev2",
+    "pageindex==0.3.0.dev3",
     "markitdown[docx,pptx,xlsx,xls]==0.1.5",
     "trafilatura==2.0.0",
     "click==8.4.0",