fix: validate pattern filter types

[darrenhalden537-lang]

Summary

• validate pattern_filter input before string/glob/regex matching
• return a clear IDAError for non-string filters instead of an AttributeError from .startswith
• add focused unit coverage for non-string rejection plus existing string/glob/regex behavior

Context

This covers one of the low-risk pre-flight mitigations discussed in #235: malformed/non-string filter inputs should fail before entering pattern matching.

Tests

• python -m py_compile src/ida_pro_mcp/ida_mcp/utils.py tests/test_utils_pattern_filter.py
• uv run pytest tests/test_utils_pattern_filter.py tests/test_server_transport.py -q

Note: I also tried uv run pytest tests/test_utils_pattern_filter.py tests/test_worker_lifecycle.py tests/test_server_transport.py -q; the new filter tests passed, but two pre-existing worker lifecycle timing tests failed locally on the unmodified origin/main timing behavior.