docs: verify Cursor sandbox network troubleshooting

[JJasonSun]

Summary

Update the Cursor troubleshooting guide with a workspace domain rule and Node proxy setting that keep the sandbox enabled. Correct the settings path for Cursor 3.21.16 and remove the outdated screenshot from the guide.

Allow the CALL-E host in the workspace → use the sandbox proxy in Node → list MCP tools

The documentation check now permits omitting installation commands from this troubleshooting page; it still rejects the existing install example when its global flag is missing.

Evidence

• Before: In the local Cursor test on September 22, curl returned CONNECT tunnel failed, response 403. After allowing the host, the Node CLI still returned fetch failed.
  After: With the documented domain rule and NODE_USE_ENV_PROXY=1, mcp tools returned ok: true, including plan_call, run_call, and get_call_run. CURSOR_SANDBOX=seatbelt confirmed the macOS sandbox remained enabled; TLS verification remained enabled.
• Runtime evidence: Cursor 3.21.16, Node 26.8.2, CALL-E CLI 0.5.2. Reused an existing login; fresh OAuth login and skill installation were not tested.
• Repository checks: pnpm check and pnpm test using pnpm 10.18.3. One Windows-only test is skipped on macOS.
• Checked the changed Markdown's JSON blocks, local links, and existing Cursor section anchor. Searched README, install guides, packages, and skills for duplicate instructions; the README already links to this guide.

Merge Danger

Only troubleshooting guidance and its repository check change. No CLI behavior or API contract changes. Reverting the commit restores the previous guidance. Users should merge the domain entry into existing workspace settings rather than replace them.

No release needed: the guide and private package's check/tests are not published package output. No package version bump or changeset is needed.