Resolve localhost preview URLs for remote environments

[juliusmarminge]

Summary

• Rewrite localhost and schemeless preview URLs to the remote environment host when the environment is reachable on a private network.
• Extend private host detection for Tailscale CGNAT and private/link-local IPv6 addresses while preserving local loopback behavior.
• Apply the same URL resolution path to preview automation opens and reused-tab navigation.
• Add resolver coverage for remote IPv4, schemeless localhost, local loopback, public relay rejection, and IPv6 hosts.

Testing

• vp test apps/web/src/browser/browserTargetResolver.test.ts

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Note

Medium Risk
Changes preview navigation URL rewriting for remote environments; wrong host classification could send traffic to the wrong target or break local vs remote behavior.

Overview
Loopback preview URLs (localhost, 127.x, schemeless hosts) are now rewritten to the connected environment’s private host when that environment is remote, keeping path, query, hash, and credentials. Local loopback environments still navigate directly without remapping.

browserTargetResolver gains shared resolveEnvironmentPortTarget logic for port and URL targets, treats the full 127.0.0.0/8 range as local, and broadens private-network detection (Tailscale 100.64/10, IPv6 ULA/link-local). Public relay hosts reject localhost URL navigation the same way as environment-port opens.

Preview automation resolves URLs once up front for new opens and reused-tab navigation. resolveDiscoveredServerUrl delegates through the URL resolver instead of duplicating port logic. Tests cover remote IPv4/IPv6, credentials, schemeless URLs, local loopback, and relay rejection.

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Note

Resolve localhost preview URLs to the remote environment host for non-local environments

• When a browser navigation target or automation open request uses a loopback URL (e.g. http://localhost:3000), the resolved URL now substitutes the remote environment's private host and port instead of navigating literally to localhost.
• Credentials, path, query, and hash are preserved during remapping. Navigation stays direct when both the requested host and the environment host are loopback.
• Extends private-network detection in isPrivateNetworkHost to cover .local/.ts.net hostnames and additional IPv4/IPv6 private ranges (ULA, link-local, CGNAT, etc.).
• resolveDiscoveredServerUrl is simplified to delegate to resolveBrowserNavigationTarget, keeping behavior consistent across all callers.
• Behavioral Change: automation open commands now receive the resolved environment-aware URL rather than the raw input URL when the environment is remote.

^{Macroscope summarized 5c215da.}

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[macroscopeapp]

Approvability

Verdict: Needs human review

This PR changes runtime behavior by mapping localhost preview URLs to remote environment hosts when connected remotely. While well-tested and by a trusted author who owns this code, the URL resolution behavior change in the preview system warrants human review.

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