### What problem does this PR solve?
Resolves#12105
This PR fixes two MCP tool call issues in
`common/mcp_tool_call_conn.py`.
First, the timeout passed to `tool_call(..., timeout=...)` was only
applied to the outer `future.result(...)` wait, but was not forwarded to
the internal MCP request. As a result, callers could pass a longer
timeout while the actual MCP request still failed after the default
internal timeout.
Second, the MCP tool call result handling assumed `result.content[0]`
always existed. If an MCP server returned an empty content list, this
could raise an exception unexpectedly.
This PR fixes both issues by:
- forwarding the external `timeout` value to the internal MCP request
timeout
- returning a clear message when the MCP server returns empty content
instead of indexing into an empty list
### Type of change
- [x] Bug Fix (non-breaking change which fixes an issue)
- [ ] New Feature (non-breaking change which adds functionality)
- [ ] Documentation Update
- [ ] Refactoring
- [ ] Performance Improvement
- [ ] Other (please describe)
### What problem does this PR solve?
As title.
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
Co-authored-by: Liu An <asiro@qq.com>
