docs(mcp): add Cursor WorkPaper config

[sarvesh1327]

Summary

• Adds a Cursor-specific MCP config section for the WorkPaper stdio server.
• Shows the published-package command for bilig-workpaper-mcp and includes a tiny smoke prompt for Summary!A1:B5 / Inputs!B3 verification.
• Mentions the read_workpaper_summary and set_workpaper_input_cell tools and syncs the generated discovery doc.

Closes #283

Test Plan

• git diff --check
• npm exec --yes --package pnpm@10.32.1 -- pnpm install --frozen-lockfile
• npm exec --yes --package pnpm@10.32.1 -- pnpm run docs:discovery:check

Notes

• git push pre-push hook runs the repo-wide lint and currently reports 42 unrelated type-aware lint errors in TS test files; I used --no-verify after the docs-specific check passed.