fix(schematic): respect intentional unconnected pins - #267

Summary

Stop validate_component_connections from reporting intentionally unconnected symbol pins and pins belonging to other units, and make its existing ignore_power_pins option effective.

Refs #182

Root cause and approach

The validator used the unit-agnostic pin extractor, discarded each library pin's electrical type, and never read ignore_power_pins. As a result it superimposed pins from other units and treated declared no-connect and optionally ignored power pins as missing connections.

• Preserve each embedded library pin's KiCad electrical type.
• Exempt pins typed no_connect and ordinary pins carrying a schematic no-connect marker.
• Honor ignore_power_pins for power_in and power_out pins.
• Use the existing unit-aware extractor so a placed unit does not inherit another unit's pins.
• Add pin_type to each finding and clarify the public tool description.

This keeps the smaller #267 framing selected by the maintainer. #280 is now closed as its duplicate. #272 continues to cover the other analysis/export/review paths.

Compatibility and safety

The request schema is unchanged. Findings gain an additive pin_type field. Results intentionally stop containing library-declared NC pins, ignored power pins, and pins from unplaced units.

The validator is read-only and does not alter the schematic.

Validation

After rebasing this one-commit PR onto current main (2183267), all commands required by CONTRIBUTING.md pass on this exact branch:

• cargo test --workspace --locked --lib --tests
• cargo test --workspace --locked --doc
• cargo clippy --workspace --locked --all-targets -- -D warnings
• cargo fmt --all -- --check

Live-GUI tests remain intentionally ignored by the upstream suite unless a running KiCad GUI/socket is supplied.

Risk and rollback

The main behavioral risk is filtering a pin that should still be reported. Regression tests cover declared NC pins, schematic no-connect markers, power filtering, selected units, and mid-wire junction behavior. Rollback is a single focused commit.