Mock policy server: Add onboarding page

[joshspicer]

Summary

• add dedicated Setup and Policies pages to the mock policy server
• guide users through the recommended system proxy workflow and the Code OSS override alternative
• automatically detect the active connection method and show its status globally
• add exact VS Code Command Palette guidance, cache recovery steps, and responsive accessible styling

Validation

• npm run eslint -- scripts/mock-policy-server/server.ts scripts/mock-policy-server/public/app.ts
• npm run stylelint -- scripts/mock-policy-server/public/style.css
• git diff --check
• verified the proxy marker response and probe isolation from Live Requests
• browser-tested Setup and Policies in dark/light themes and desktop/narrow layouts
• verified Code OSS override apply/restore preserves the original file

[Copilot]

Pull request overview

Adds onboarding and connection detection to the mock policy server.

Changes:

• Introduces Setup and Policies pages with responsive, accessible styling.
• Detects system-proxy and Code OSS override connections.
• Expands setup, command, and cache-recovery guidance.

Show a summary per file

File	Description
server.ts	Adds proxy-probe responses and marker headers.
README.md	Documents onboarding and connection workflows.
style.css	Styles the new responsive UI.
index.html	Adds Setup/Policies page structure.
app.ts	Implements navigation and connection detection.

Review details

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• Files reviewed: 5/5 changed files
• Comments generated: 2
• Review effort level: Balanced