docs(package): pipx CPU torch swap that works, and the local vector-store path note

- pipx: replacing the CUDA torch inside the pipx environment needs
  pip's --force-reinstall (pipx inject, with or without --force, leaves a
  satisfied requirement alone), and --no-deps so torch's dependencies are not
  reinstalled from the PyTorch index, which carries older copies of them.
- Upgrading: the embedded Milvus and LanceDB default paths now resolve under
  the checkout (or DOCSGPT_HOME) instead of the start directory; the note
  names the old location and the settings to pin.

docs/content/Deploying/Pip-Install.mdx

@@ -41,7 +41,11 @@ pip install --index-url https://download.pytorch.org/whl/cpu torch torchvision
 pip install "docsgpt[docling]"
 ```
 
-`uv pip install` accepts the same two commands. With `pipx`, install `docsgpt[docling]` and then run `pipx inject --index-url https://download.pytorch.org/whl/cpu docsgpt torch torchvision` to swap the CUDA build for the CPU one.
+`uv pip install` accepts the same two commands. With `pipx`, install `docsgpt[docling]` first, then replace the CUDA build inside its environment (`--no-deps` keeps pip from touching torch's dependencies, which the PyTorch index carries in older copies):
+
+```bash
+pipx runpip docsgpt install --force-reinstall --no-deps --index-url https://download.pytorch.org/whl/cpu torch torchvision
+```
 
 ## Configure
 

docs/content/upgrading.mdx

@@ -111,6 +111,16 @@ alias, so nothing breaks on upgrade, but update these before the alias goes:
   than it would have (a monthly sync by up to a month). Nothing to do.
 - Data directories do not move: the compose files keep your indexes, inputs
   and vectors under `application/` in the checkout, where they already are.
+- The backend is also a package now (`pip install docsgpt`, see
+  [Install with pip](/Deploying/Pip-Install)). Runtime data lives in a data
+  home: `DOCSGPT_HOME`, else the checkout, else the directory the process
+  starts in. One consequence for a source checkout: the embedded Milvus
+  (`MILVUS_URI`) and LanceDB (`LANCEDB_PATH`) default paths now resolve under
+  the checkout instead of the start directory. If you use either store at its
+  default path and start DocsGPT from another directory, the old data is at
+  `<start directory>/milvus_local.db` or `<start directory>/data/lancedb`;
+  point the setting at it, or move it into the checkout. Faiss indexes and
+  uploads were already stored under the checkout and are unaffected.
 
 ## Check your version