[phsauter]

Summary

I have some cases where we have coloring on the lowest two metals and pins can be in both but we really only want to route on the third and above to avoid coloring.
Currently OpenROAD skips via alignment on the layers below the first routing layer, eg metal layer 2 in my case. This enables it without enabling general routing on those layers.

Type of Change

• New feature

Impact

Improved pin access when going through one intermediate non-routing layer.

Verification

• I have verified that the local build succeeds (./etc/Build.sh).
• I have run the relevant tests and they pass.
• My code follows the repository's formatting guidelines.
• I have included tests to prevent regressions.
• I have signed my commits (DCO).

[gemini-code-assist]

Code Review

This pull request modifies the default via initialization logic in io::Parser::initDefaultVias to check for a non-null default via definition on the layer instead of comparing the layer number against the bottom routing layer. It also introduces a new set of unit tests in parserTest.cpp to validate default via generation and retention behavior under various configurations. The feedback suggests calling the base class Fixture::SetUp() within the overridden SetUp() method of the new test fixture to ensure proper initialization.

[gemini-code-assist]

It is a best practice to call the base class SetUp() method when overriding it in a test fixture. This ensures that any common initialization performed by Fixture::SetUp() is executed properly.

Suggested change

	void SetUp() override
	{
	auto tech = design->getTech();
	void SetUp() override
	{
	Fixture::SetUp();
	auto tech = design->getTech();