Fixes 'exit proxy never used in chain' and 'browsers break when chain is green'. Chain Builder gets a Save-as-final-hop button that appends the typed exit proxy to the manual chain. On engage, Chromium browsers get pinned to our proxy via HKLM policy (ProxyMode=fixed_servers, ProxyServer, ProxyBypassList) and QuicAllowed=0 so HTTP/3 doesn't bypass HTTP proxies and stall under the kill-switch. Chain start now runs check_https_tunnel and warns clearly when proxies forward HTTP but refuse CONNECT — the real cause of green-chain-yet-blank-browser.
Co-authored-by: Cursor <cursoragent@cursor.com>
On Server / GPO baselines, ProxySettingsPerUser=0 makes WinINet ignore HKCU entirely. When elevated, force the flag to 1 and mirror proxy values to HKLM root + Connections blob. Detect Group Policy proxy locks and surface them so the user knows browsers will keep the policy value. Add diagnose_system_proxy() logged on every chain engage.
Co-authored-by: Cursor <cursoragent@cursor.com>
