Fix issue 28 with tool use and improve the logic overall

[a-akimov]

Motivation and Context

• Fix process_query in mcp-client-python/client.py so tool-use turns conform to the Anthropic Messages API: append the assistant's full content (preserving the tool_use block) and reply with a proper tool_result block carrying tool_use_id, replacing the previous plain-user-message workaround and the dead hasattr(content, "text") check that the API spec confirms can never be true.
• Restructure the response handler into a turn-level loop so the client correctly handles parallel tool calls in a single response (executing all tool_use blocks and returning all matching tool_result blocks in one user message) and chained tool calls across turns (passing tools on every follow-up request so the model can keep using them).
• Add MAX_TOOL_TURNS = 10 cap to prevent unbounded tool-use loops; on cap-hit the client appends a [Stopped after N tool-use turns] notice and returns the accumulated output.
• Fix chat_loop to exit cleanly on EOFError / KeyboardInterrupt instead of being swallowed by a broad except Exception and respinning forever. This also makes the python client smoke test pass reliably under non-tty stdin regardless of whether ANTHROPIC_API_KEY is set (previously the test hung whenever the key was loaded from .env).

How Has This Been Tested?

• tests/smoke-test.sh passes locally (all 5 tests green, no hangs) both with and without ANTHROPIC_API_KEY set.
• Manual: run client.py against weather-server-python with a real ANTHROPIC_API_KEY and ask a query that triggers a single tool call (e.g. "What's
  the weather in NYC?") — verify the model receives the tool result and produces a final answer.
• Manual: ask a query that triggers multiple sequential tool calls (e.g. "Compare the weather in NYC and SF") — verify all calls execute and the final answer references both results.
• Manual: verify the MAX_TOOL_TURNS cap path by lowering the constant locally and confirming the [Stopped after N tool-use turns] notice appears.
• Manual: press Ctrl+D or Ctrl+C at the Query: prompt — verify the client exits cleanly instead of spinning.

Breaking Changes

N/a

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

Fixes issue #28.