[Bug]: [MCP/CLI] Bare loopback IP addresses (127.0.0.1:port) and hosts with ports fail to navigate due to erroneous scheme inference

Finding: In Playwright CLI/MCP (open, tab-new, browser_navigate), a reporter says that schemeless loopback IP targets such as 127.0.0.1:3000 are navigated as https:// and fail with net::ERR_SSL_PROTOCOL_ERROR, and that bare host:port values such as example.com:8080 abort with net::ERR_ABORTED; affected version is stated only as Playwright main as of 2026-10-10 [https://github.com/microsoft/playwright/issues/43263]. Reported symptoms: The issue gives the error text 'page.goto: net::ERR_SSL_PROTOCOL_ERROR at https://127.0.0.1:3000/' for loopback addresses (127.0.0.1, 0.0.0.0, [::1]) and 'net::ERR_ABORTED at example.com:8080' for a bare host with port [https://github.com/microsoft/playwright/issues/43263]. Reporter's proposed cause (not maintainer-confirmed): The reporter points at checkUrlAndNavigate in packages/playwright-core/src/tools/backend/tab.ts. As described, it tries new URL(url) and, on a throw, prepends http:// only when the string starts with localhost, otherwise https://. Per the reporter, IP-literal inputs throw and so fall through to https://, which breaks plain-HTTP dev servers. For host:port inputs beginning with a letter, the reporter says new URL() succeeds by treating the host as a scheme, so the catch branch is skipped and no scheme is added [https://github.com/microsoft/playwright/issues/43263]. This URL-parsing analysis was not independently verified here. Possible mitigation (source-backed inference, not verified by KFA): Because the reported failure arises from scheme inference on schemeless input, supplying an explicit scheme such as http:// for local servers should avoid the inference path. The issue itself lists only the expected behavior (loopback defaults to http://, other bare hosts to https://) and does not present a tested workaround [https://github.com/microsoft/playwright/issues/43263]. Status: The issue is open, with no comments, no maintainer response, no linked fix commit and no released fix in the supplied data. The reporter references a screenshot of fixed behavior, which was not inspected. Limitation: This is a single external report with no KFA reproduction. Treat the cause as a hypothesis until maintainers or code inspection confirm it.