Stage and require verified extraction helper in Windows release packages

docs/BUILDING.md

@@ -27,6 +27,7 @@ python -m pip install cmake
 python tools/embeddinggemma2/build_runtime.py --backend cpu --jobs 2
 python tools/embeddinggemma2/stage_runtime.py --backend cpu
 python tools/media-runtime/provision.py --stage
+python tools/stage_extraction_worker.py
 python tools/embeddinggemma2/download.py
 $env:SEARCHI_FORCE_CPU = '1'
 $env:SEARCHI_GEMMA_MODEL_DIR = (Resolve-Path .searchi/models/embeddinggemma2).Path
@@ -297,3 +298,9 @@ Windows and Linux x86-64 startup and CPU decoding have executed here;
 other architectures and macOS decoder packaging remain gates.
 See [media runtime provenance](../tools/media-runtime/README.md) and
 [measured media limitations](MEDIA-QUALITY.md).
+
+PDF/DOCX indexing requires the bundled `searchi-extract-worker`. Build and stage
+it with `python tools/stage_extraction_worker.py` before desktop development or
+release packaging. Release builds reject a missing helper. Headless deployments
+place the platform helper beside the CLI executable. Parser failure retains
+filename search and exposes an extraction error; there is no in-process fallback.