docs: verify compatibility through pi-coding-agent 0.85.1

[auchan]

Summary

• verified Pi on Code against @earendil-works/pi-coding-agent@0.85.1 (full VS Code integration suite, 241 passing)
• updated the documented supported range to Pi 0.80.8 – 0.85.1 and the install command to @0.85.1 (README + README.zh-CN)
• normalized CRLF when reading the sidebar source in session-menu-backdrop.test.ts so it also passes on Windows checkouts

Validation

• bun run check-types
• bun run lint
• bun run compile-tests
• xvfb-run -a bun x vscode-test (241 passing)
• git diff --check