update-to-use-yarn-4.10.3

[cameronvoell]

Update package manager to Yarn 4.10.3 and require Node.js >=22

• Pins Yarn 4.10.3 by committing the release script to .yarn/releases/yarn-4.10.3.cjs and setting yarnPath in .yarnrc.yml, using the node-modules linker.
• Adds "packageManager": "yarn@4.10.3" to package.json for Corepack compatibility and bumps the engines.node requirement from >=20 to >=22.
• Updates .gitignore to preserve .yarn/releases while ignoring cache, unplugged, and state files.
• Adds setup instructions to CONTRIBUTING.md and README.md directing contributors to enable Corepack.
• Risk: projects running Node 20 will no longer satisfy the engines field.

^{Macroscope summarized 3e3d91c.}

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Latest commit: 3e3d91c

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[cameronvoell]

• adds the ability to run example app tests against d14n testnet staging #774
• 5.7.0 Release - add new device sync functions and tests for libxmtp release 1.10.0 #773
• update-to-use-yarn-4.10.3 #772 👈 (View in Graphite)
• main

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[macroscopeapp]

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