[Doc] Fix macOS installation dependency resolution issue (vllm-project#26721)

Signed-off-by: faisal shah <[email protected]>

Author: shahfasal

docs/getting_started/installation/cpu.apple.inc.md

@@ -28,10 +28,15 @@ After installation of XCode and the Command Line Tools, which include Apple Clan
 ```bash
 git clone https://github.com/vllm-project/vllm.git
 cd vllm
-uv pip install -r requirements/cpu.txt
+uv pip install -r requirements/cpu.txt --index-strategy unsafe-best-match
 uv pip install -e .
 ```
 
+!!! tip
+    The `--index-strategy unsafe-best-match` flag is needed to resolve dependencies across multiple package indexes (PyTorch CPU index and PyPI). Without this flag, you may encounter `typing-extensions` version conflicts.
+    
+    The term "unsafe" refers to the package resolution strategy, not security. By default, `uv` only searches the first index where a package is found to prevent dependency confusion attacks. This flag allows `uv` to search all configured indexes to find the best compatible versions. Since both PyTorch and PyPI are trusted package sources, using this strategy is safe and appropriate for vLLM installation.
+
 !!! note
     On macOS the `VLLM_TARGET_DEVICE` is automatically set to `cpu`, which is currently the only supported device.