Add normalize_pin() for consistent int/str coercion at YAML boundary,
resolve_pin() for label-to-number resolution, and fix GraphViz port
index rendering for loops and shorts on non-sequential connectors.
Key changes:
- wv_utils: add normalize_pin(), reject floats/bools, refactor expand()
- wv_dataclasses: normalize pins/pinlabels/wirelabels in __post_init__,
add Connector.resolve_pin(), resolve loop/short pins through labels,
detect duplicate pins and minimum pin count in loops/shorts
- wv_graphviz: convert pin IDs to position indices in loop/short edges,
fix short membership test from pin.index to pin.id
- wv_harness: delegate connect() pin resolution to resolve_pin()
- tests: 50 tests covering resolution, coercion, rendering, validation
