docs: clarify macOS onboarding and troubleshooting

[udita-0707]

Problem

macOS local setup can fail with unclear or inconsistent errors for new contributors.

• The repository currently works best with Node.js 24.x and pnpm 10.26.x, but this is not clearly surfaced in the onboarding flow.
• Using pnpm 11.x may result in engine mismatch errors.
• Homebrew-installed pnpm can conflict with nvm-managed installations.
• After switching versions, zsh may continue using a cached binary path unless hash -r is run.
• Builds may fail with JavaScript heap out of memory.
• The README currently lacks a concise contributor-focused local development setup section.

Why This Helps

• Reduces onboarding friction for first-time contributors.
• Provides copy-pasteable setup and verification commands.
• Helps contributors quickly diagnose common environment issues.
• Keeps README.md concise while moving detailed troubleshooting guidance into CONTRIBUTING.md.
• Keeps the scope documentation-only and easy to review.

Changes Made

README.md

Added:

• Recommended Node.js version (24.x)
• Recommended pnpm version (10.26.x)
• Quick setup instructions using nvm and corepack
• Version verification commands
• A short pnpm compatibility note
• Expanded build memory workaround guidance

CONTRIBUTING.md

Added:

• Local environment troubleshooting guidance
• hash -r shell refresh instructions
• Homebrew vs nvm pnpm path guidance
• Version verification and debugging commands
• Additional build memory troubleshooting notes

.nvmrc

Updated:

• .nvmrc to use 24 for a simpler and more consistent local setup experience.

Scope

• Documentation-only changes
• No runtime or dependency changes
• No package.json modifications

Tested On

• macOS
• Node.js 24.x
• pnpm 10.26.x

[gemini-code-assist]

Code Review

This pull request updates the Node.js and PNPM prerequisites and adds macOS-specific troubleshooting documentation in CONTRIBUTING.md and README.md. It recommends Node 24.x and PNPM 10.26.x to avoid engine mismatch errors, and increases the default NODE_OPTIONS heap size limit to 8192 for macOS/Linux. Feedback was provided to update the global PNPM installation command in CONTRIBUTING.md to target version 10 explicitly, preventing contributors from accidentally installing an incompatible version.

Important

The consumer version of Gemini Code Assist on GitHub is being sunset. Starting June 18, 2026, new organization installations will be blocked, and all code review activity will officially cease on July 17, 2026.
For more details on the timeline and next steps, please review the Help Documentation.

[udita-0707]

@HenryHengZJ can you please have a look and review this PR