feat(client): add privacy-safe request history

[Ritwij Aryan Parmar (RitwijParmar)]

Summary

Adds a bounded request history on MCPClient so client users can debug slow, failed, or repeated MCP calls without retaining request payloads, tool arguments, resource URIs, prompt arguments, or result bodies.

The history records method, result type, session id, duration, success or failure, and error class/message. Convenience methods still call the underlying ClientSession helpers, with metadata recorded around those calls.

Why

When MCP apps run multiple tools or remote sessions, the current client surface makes it hard to answer simple questions like which request failed, how long it took, and whether the same operation repeated. This gives that debugging surface while keeping sensitive tool arguments out of memory snapshots and logs.

Testing

• uv run pytest tests/test_client.py --no-cov
• uv run ruff check --select I,RUF022 src/dedalus_mcp/client/__init__.py src/dedalus_mcp/client/core.py src/dedalus_mcp/client/diagnostics.py
• uv run ruff check --select D202,EM,TRY src/dedalus_mcp/client/diagnostics.py

uv run mypy src/dedalus_mcp/client could not run locally because mypy is not installed in the environment.

AI assistance was used to prepare this PR. I reviewed the code and tests before submitting.