Use safe project source-set dependencies

Replace direct Groovy compileOnly project(':path').sourceSets.main.runtimeClasspath declarations with the project's consumable runtimeElements dependency and task-backed main output. This retains classes, resources and runtime dependencies without resolving another project's configuration, which Gradle 9 forbids during parallel execution. Other non-resolving sourceSets reads use an explicit Project lookup. Only literal absolute paths in unshadowed canonical dependencies configurations are migrated; ordinary project dependencies are retained.