docs: add version 1.0.0 badge, CHANGELOG, and changelog maintenance rule

CHANGELOG.md

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+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
+
+## [1.0.0] - 2026-02-10
+
+### Added
+
+- **arkts-development** skill
+  - ArkUI declarative UI framework guide
+  - State management V1 decorators (@State, @Prop, @Link, @Provide/@Consume, @Observed/@ObjectLink)
+  - State management V2 decorators (@ComponentV2, @Local, @Param, @Event, @ObservedV2, @Trace, @Computed, @Monitor, @Provider/@Consumer)
+  - Component lifecycle and navigation (router)
+  - Network requests (http) and local storage (preferences)
+  - TypeScript to ArkTS migration guide
+  - Code templates: component-template.ets, list-page-template.ets, state-management-v2-examples.ets
+  - Reference docs: API reference, component patterns, ArkGuard obfuscation, CodeLinter, hstack, hvigorw command-line
+- **harmonyos-build-deploy** skill
+  - hvigorw build commands (assembleApp, assembleHap, assembleHsp, assembleHar)
+  - ohpm dependency management
+  - hdc device installation and management
+  - Troubleshooting common build/deploy errors
+  - Device installation reference guide
+- **AGENTS.md** with coding conventions and documentation guidelines