GitHub MCP connector returns "[non-text content: resource]" instead of file body in voice mode only

GitHub MCP connector's `get_file_contents` returns no file body in voice mode only (claude.ai).

## Steps to reproduce

1. Start a voice-mode conversation on claude.ai with the GitHub MCP connector enabled.
2. Ask it to read any text file (reproduces with `README.md` in the public repo `github/github-mcp-server`).
3. The tool result shows `successfully downloaded text file` and the correct blob SHA, but the body is replaced with `[non-text content: resource]`.
4. Switching the same session to text mode succeeds; switching back to voice mode fails again.

## Observations

- Not file/repo specific; the same file that fails in voice mode succeeds in text mode within the same session.
- The blob SHA is returned correctly, so GitHub responds fine — the resource-format content appears to be dropped on the client side in voice mode.
- Write tools (`create_or_update_file`) work in voice mode.
- The Google Drive connector reads md file bodies fine in voice mode.
- Workaround: `get_commit` with `detail: "full_patch"` retrieves the full content via unified diff.

## Environment

Reproduces on the iPhone app, the Mac desktop app, and Chrome on macOS — voice mode always fails, text mode never does. First observed 2026-08-31, reproduces every time. Plan: personal Max.

## Related reports

- Reported to GitHub as well: https://github.com/github/github-mcp-server/issues/3189 (but the client-side voice-mode tool-result handling is the likely cause, since only the receiving side changes between modes).
- Submitted via Claude Code `/feedback`, Feedback ID: `3905a4b7-f995-4918-b2bf-bd6cccec4e7a`.
- Also reported to Anthropic support via the in-app messenger.