Implemented MCP input uploads in `code/`. GitHub credentials were inaccessible in this environment, so no PR was opened.

Send your engineering team [mcp-input-uploads.patch](mcp-input-uploads.patch) and the prepared [PR description](PR.md).

The new `upload_input` tool accepts text or Base64 binary files after `add_task` or `add_case`. It preserves relative paths, replaces existing files at the same path, and makes inputs available through `get_case`, runner bundles, and benchmark exports. Uploads use the existing owner/editor permissions and benchmark scope.

Assumptions: one file per call, a 25 MiB decoded limit, and clients supply actual file contents. Larger or chunked uploads and fetching files from URLs are outside this patch. Client/proxy limits may be lower.

Apply from a clean checkout of `EveryInc/checks`:

```sh
git switch -c add-mcp-input-uploads 18df437ab76efbc91c4c7796959be20c489049e9
git apply --check /path/to/mcp-input-uploads.patch
git apply /path/to/mcp-input-uploads.patch
```

Verified: clean patch application against the supplied archive, syntax for all 12 changed Ruby files, and 6 isolated validation tests with 46 assertions. **Rails integration/model tests and RuboCop remain unverified:** dependencies were unavailable and the sandbox could not reach RubyGems. Thirteen regression tests are included. See [VALIDATION.md](VALIDATION.md) for commands and evidence.