fix: grant coder user write permission to rbenv versions directory

This fixes the issue where gem install fails with permission denied and
bundler cannot install git gems due to missing write access to
/opt/rbenv/versions.

Author: ide-coder

Dockerfile

@@ -228,7 +228,8 @@ RUN /opt/conda/bin/conda config --set show_channel_urls yes
 # Set ownership for coder user
 RUN chown -R coder:coder /home/coder \
     && chown -R coder:coder /opt/conda \
-    && chown -R coder:coder /opt/go-tools
+    && chown -R coder:coder /opt/go-tools \
+    && chown -R coder:coder /opt/rbenv/versions
 
 # Create entrypoint script that initializes home directory on container start
 # This ensures configs are properly set when /home/coder is mounted externally