chore(docker): pre-install @ai-sdk/anthropic in opencode config dir

Required by the custom minimax provider in opencode.json which uses
@ai-sdk/anthropic to hit minimax's Anthropic-compatible API endpoint.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Dockerfile

@@ -66,8 +66,10 @@ ARG USER_GID=1000
 WORKDIR /app
 COPY --chown=node:node --from=build /app /app
 RUN npm install --global --omit=dev @anthropic-ai/claude-code@latest @openai/codex@latest opencode-ai @google/gemini-cli \
-  && mkdir -p /paperclip \
-  && chown node:node /paperclip
+  && mkdir -p /paperclip/.config/opencode \
+  && cd /paperclip/.config/opencode \
+  && npm install @ai-sdk/anthropic \
+  && chown -R node:node /paperclip
 
 COPY scripts/docker-entrypoint.sh /usr/local/bin/
 RUN chmod +x /usr/local/bin/docker-entrypoint.sh