fix(analysis): exclude Foundry showmap replay from cumulative inventory

[haileymarshall]

The cumulative inventory path walks every *.log file, while the event parser excludes foundry_showmap.log:

if not path.is_file() or not path.name.endswith(".log"):
    continue

Given a replay-only logs directory, build_cumulative_rows(..., logs_dir=...) emitted [("foundry", "run-1:i-abcd1234", 0.0, 0)] even though no benchmark log was parsed.

Fix

Add foundry_showmap.log to the cumulative inventory ignore set so zero-event seeding follows the same input filter as event, throughput, and progress parsing.

Tests

Added a regression test covering a replay-only directory. It fails on main with an AssertionError because the unexpected row above is emitted; with this change the test passes.

Validation

• uv run --with-requirements analysis/requirements.txt python -m unittest discover -s analysis/tests -p 'test_*.py': 133 tests, OK.
• python3 -m compileall -q analysis scripts: passed.
• git diff --check: passed.
• Baseline before the change: 132 tests, OK.
• Terraform formatting and docs build were not run locally because Terraform is unavailable and Node dependencies are not installed.