Quieter debug logging

• Remove the "negative constant passed to .trailing/.bottom/.right" debug warning. Auto-negation turns a negative constant into an outward overhang (a decorative badge poking out of a card corner, for example) — legitimate layout intent that is indistinguishable from a mistyped inset, so the warning fired on every layout pass for correct code
• Deduplicate the remaining debug warnings: each distinct message is now printed once per process. update() is routinely driven from animations, scroll handlers and keyboard callbacks, where a single missed anchor previously flooded the console every frame
• 448 tests passing