feat: add bazel-codex entry to justfile (#9177)

This is less straightforward than I realized, so created an entry for
this in our `justfile`.

Verified that running `just bazel-codex` from anywhere in the repo uses
the user's `$PWD` as the one to run Codex.

While here, updated the `MODULE.bazel.lock`, though it looks like I need
to add a CI job that runs `bazel mod deps --lockfile_mode=error` or
something.

justfile

@@ -44,6 +44,13 @@ install:
 test:
     cargo nextest run --no-fail-fast
 
+# Build and run Codex from source using Bazel.
+# Note we have to use the combination of `[no-cd]` and `--run_under="cd $PWD &&"`
+# to ensure that Bazel runs the command in the current working directory.
+[no-cd]
+bazel-codex *args:
+    bazel run //codex-rs/cli:codex --run_under="cd $PWD &&" -- "$@"
+
 bazel-test:
     bazel test //... --keep_going