docs: add CLAUDE.md with build commands and architecture overview

[Naturalclar]

Overview

Adds a CLAUDE.md at the repo root so AI coding agents (Claude Code and similar) start with accurate context about this repository instead of rediscovering it each session.

It captures two things:

Commands — the Yarn 4 script set, how to run a single Jest test, and a note that linting/formatting is Biome (biome.json, tabs + double quotes) even though the CI step is named "ESLint Checks". It also records that the JS test suite is a placeholder and the real CI validation is native compilation for both architectures.

Architecture — the parts that only become clear after reading several files together:

• src/index.tsx is a thin wrapper (recursive processColor + actionsHash), and why actionsHash exists — the new architecture receives actions as a C++ struct array that is impractical to deep-compare, so native code compares the hash string instead.
• The two type definitions are deliberate: src/types.ts is the public API, while src/NativeModuleSpecs/UIMenuNativeComponent.ts is the codegen spec whose inline SubAction/MenuAction duplication must not be refactored away. Adding a prop means touching both, plus ios/MenuViewManager.mm.
• The iOS Shared / NewArch / OldArch layout, with FabricViewImplementationProtocol as the seam and the iOS 13 action-sheet fallback.
• The Android three-way manager split — MenuViewManagerBase, the per-architecture MenuViewManagerSpec, and the RN-version-patched MenuViewManager selected via sourceSets because of the setBorderColor signature change — plus new arch being force-enabled at RN >= 0.82. This mirrors the versioning guidance already in CONTRIBUTING.md.
• That example/ is generated by react-native-test-app, which is why yarn bootstrap is a prerequisite rather than a convenience.

Docs only — no source, build, or configuration files are changed.

Test Plan

Nothing to exercise at runtime; the change adds a single Markdown file and touches no code paths.

Verification performed:

• Every command documented was read directly from package.json scripts, .github/workflows/ci.yml, and CONTRIBUTING.md rather than assumed.
• Architecture claims were checked against the files they describe: src/index.tsx, src/utils.ts, src/types.ts, src/NativeModuleSpecs/UIMenuNativeComponent.ts, the three src/UIMenuView*.tsx variants, ios/MenuViewManager.mm, ios/NewArch/MenuView.mm, ios/NewArch/FabricViewImplementationProtocol.swift, ios/Shared/MenuViewImplementation.swift, android/build.gradle, android/src/main/java/com/reactnativemenu/MenuViewManagerBase.kt, both MenuViewManagerSpec.kt variants, and both reactNativeVersionPatch copies of MenuViewManager.kt (the setBorderColor difference was confirmed by diffing them).
• CI on this PR should stay green — lint, tsc, and the Android/iOS builds do not read Markdown.

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Generated by Claude Code