docs: clarify Yarn 4 setup and contributor onboarding

[Priyans00]

Proposed changes (including videos or screenshots)

Clarifies that the repository uses Yarn 4 (Berry), recommends Corepack for Yarn
management, adds a short Windows note about long path support, and documents that
peer dependency warnings during install are expected.

This is a documentation-only change intended to improve contributor onboarding.

Issue(s)

Closes #1812

Further comments

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Latest commit: c800403

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