Add differential coverage relscore support

[decofe]

Summary

• run Foundry showmap replay after the normal fuzz campaign and upload AFL showmap files with logs
• compute differential coverage relscores from showmap campaign directories during analysis
• include filtered-analysis support, methodology docs, and unit tests

Tests

• uv run python -m unittest analysis.tests.test_differential_coverage analysis.tests.test_analyze_foundry_parser
• uv run --with-requirements analysis/requirements.txt python -m unittest discover analysis/tests
• uv run python -m py_compile analysis/analyze.py scripts/run_analysis_filtered.py analysis/tests/test_differential_coverage.py
• bash -n fuzzers/foundry/run.sh