Refactors _build_connectivity() into a two-layer state builder so the
union-find internals (pin_at, label_at, wire_segments) are accessible
to new analysis tools without duplicating the 200-line connectivity engine.
New tools:
- audit_wiring: trace all wires connected to a component, report per-pin
net membership with wire segment coordinates and connected pins
- remove_wires_by_criteria: bulk-remove wires by coordinate filters
(y, x, min/max ranges, tolerance) with dry_run preview support
- verify_connectivity: compare actual wiring against an expected
net-to-pin mapping, report matches/mismatches/missing nets
New sexp_parser utilities:
- parse_wire_segments: extract (wire ...) blocks with start/end/uuid
- remove_sexp_blocks_by_uuid: atomically remove blocks by UUID set
Root cause: kicad-sch-api doesn't back-populate comp.pins or sch.nets
on loaded schematics. All data is accessible through alternative APIs.
Pin extraction: use comp.get_symbol_definition().pins for metadata and
sch.list_component_pins(ref) for schematic-transformed positions.
Connectivity: new wire-walking engine using union-find on coordinates.
Walks wires, pin positions, labels, and power symbols to reconstruct
the net graph. Replaces broken ConnectivityAnalyzer/sch.nets fallbacks.
Eliminates 'unhashable type: Net' crash.
Hierarchy: use sch.sheets.get_sheet_hierarchy() instead of the broken
sheets.data.get("sheet", []) raw dict approach.
Labels: supplement sch.get_statistics() with sch.labels.get_statistics()
and sch.hierarchical_labels for accurate counts.
99 tests passing, lint clean.
