docs: fix contributor inspector build paths

[CooperSheroy]

Summary

• update contributor inspector commands to use the checkout's built MCP binary instead of /build at filesystem root
• clarify the MCP client config placeholder path so it includes the repository directory

Verification

• npm ci
• npm run build
• npm run check-format
• git diff --check
• checked package.json bin path for chrome-devtools-mcp matches build/src/bin/chrome-devtools-mcp.js

[google-cla]

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[nattallius]

Hi, in order for your pr to be merged, you need to sign cla.
And also your suggestion lacks support for win command line, so do can you update pr to reflect it?