Combines hierarchy-aware ERC (via root schematic resolution) with
connectivity analysis and optional baseline comparison into one atomic
call. Supports fail_on parameter to gate pass/fail on specific ERC
violation types (default: multiple_net_names). Baseline comparison
detects connection count decreases and unconnected pin increases as
regressions.
Replaces the 20+ tool call workflow of running ERC + connectivity on
each sub-sheet individually.
280/280 tests pass, ruff + mypy clean.
