Add platform badges and "Why This Skill?" section to README

docs: update README with npx skills installation instructions

feat: add README, CONTRIBUTING, and LICENSE

feat: add openai.yaml — cross-platform agent config

feat: add hygiene.md — testing, lint, and code hygiene

feat: add kotlin.md — modern Kotlin patterns for Android

feat: add performance.md — LazyList, remember, state read scope

feat: add accessibility.md — TalkBack, semantics, touch targets

feat: add design.md — Material 3 theming and adaptive layouts

feat: add navigation.md — Navigation Compose and type-safe navigation

feat: add recomposition.md — stability, derivedStateOf, key()

feat: add effects.md — side effects and effect handlers

feat: add state.md — state management and data flow

feat: add composables.md — composable structure and patterns

feat: update SKILL.md with author metadata