refactor(rules): move UI principles to topic rule

shared/rules/ui-ux/references/principles-and-priorities.md

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+# UI and UX Principles
+
+Apply these principles across interface work. Use the other UI/UX rules only for the affected screen or interaction.
+
+* Design for clarity and low cognitive load. Give each screen a clear purpose and make important actions easy to discover.
+* Prefer familiar, predictable patterns. Keep layouts calm, group related content, and use hierarchy, spacing, typography, and color consistently.
+* Minimize steps for common tasks. Remove decorative elements, choices, and interactions that do not help users complete a task.
+* Make primary actions distinct from secondary actions. Keep related information and actions close, and keep important information visible without unnecessary scrolling.
+* Every interaction adds cognitive cost. Prefer fewer clear choices and predictable behavior over clever or surprising automation.
+* Prioritize correctness, clarity, safety, accessibility, user control, task efficiency, consistency, and responsiveness before visual polish.
+* Do not let visual polish reduce readability, accessibility, or task completion.
+* If multiple UX directions remain and the choice materially changes a user's workflow or safety, ask for the decision. Make minor reversible choices independently.