Ignore deleted headerless diff paths

[chailandau]

Why

Headerless unified diffs represent deleted files with +++ /dev/null. The review parser strips the leading slash first, so it can incorrectly treat dev/null as a touched material path.

What

• Ignore /dev/null destinations before normalizing headerless diff paths
• Cover deleted and newly added files with focused parser tests
• Add a patch changeset for the public package

Risk Assessment

Low. The change only affects fallback parsing for unified diffs without diff --git headers.

Generated with Goose