Drop ENTRYPOINT in favor of CMD ["pass-cli"]

Every real caller (code.aneur.in/cloud/cloud's deploy workflows) runs a
mounted-in script against pass-cli, not bare pass-cli args, so an
ENTRYPOINT override was needed on every invocation. With no ENTRYPOINT,
`docker run this-image sh /script.sh` just replaces CMD directly.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

README.md

@@ -20,22 +20,29 @@ its own glibc environment.
 
 ## Usage
 
-The image's `ENTRYPOINT` is `pass-cli` itself:
+There's no `ENTRYPOINT` -- just `CMD ["pass-cli"]`. Run bare:
 
 ```sh
-docker run --rm code.aneur.in/cloud/pass-cli:<tag> --version
+docker run --rm code.aneur.in/cloud/pass-cli:<tag>
 ```
 
 To run your own script against `pass-cli` instead (login, fetch an item,
-parse the result, etc.), override the entrypoint and mount the script in:
+parse the result, etc.), mount it in and pass it as the command -- it
+replaces `CMD` entirely, no `--entrypoint` override needed:
 
 ```sh
 docker run --rm \
   -e PROTON_PASS_PERSONAL_ACCESS_TOKEN \
   -v "$PWD/my-script.sh:/script.sh:ro" \
-  --entrypoint sh \
   code.aneur.in/cloud/pass-cli:<tag> \
-  /script.sh
+  sh /script.sh
+```
+
+For one-off interactive use, prefix `pass-cli` explicitly, since args
+replace `CMD` rather than appending to it:
+
+```sh
+docker run --rm code.aneur.in/cloud/pass-cli:<tag> pass-cli --version
 ```
 
 `PROTON_PASS_KEY_PROVIDER` is set to `fs` in the image by default, since a