docs: clarify Cursor npx setup with PATH context and full path guidance

[staubina]

Summary

• Adds a note explaining that Cursor runs in an isolated bash environment that does not inherit the terminal's PATH, so npx cannot be resolved by name alone
• Adds a Before configuration section instructing users to verify npx is installed and find its full path before configuring the MCP server
• Changes the command value in the Cursor npx example from "npx" to "path/to/npx" to reflect that the absolute path is required

Test plan

• Verify the Cursor npx JSON snippet renders correctly in the docs
• Confirm the note and pre-configuration steps are clear and actionable for a new user

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