Adds targeted test infrastructure and validation checks to protect table drawing hooks and drop-in framework contracts against unintended modifications.
* CPTableViewDrawingTest: Verifies subclass invocation order for drawing steps and ensures application-specified background colors persist across theme-state changes.
* DropInCompatibilityTest: Validates default theme names, window control configurations, pop-up button bezel styles, and table class defaults.
* DropInSnapshot: Encapsulates theme attribute defaults, public API surface, default view construction, and window controls as structured data.
* DropInBaselineGenerator: Provides tooling to capture current framework state as a baseline.
* DropInBaselineTest: Compares framework artifacts against the established baseline, permitting additions while reporting modifications and removals.
* DropInBaseline.json: Introduces the initial compatibility baseline artifact.
