[codex] fix: preserve localhost preview hosts

[StiensWout]

Summary

• Preserve normalized localhost discovered preview URLs when the prepared connection itself is local loopback.
• Keep 0.0.0.0 flowing through the existing environment-port normalization path.
• Keep private remote host remapping for discovered loopback ports.

Root cause

resolveDiscoveredServerUrl(...) treated every loopback discovered URL as an environment-port target. When the prepared connection base was http://127.0.0.1:<port>, that remapped localhost:<port> onto 127.0.0.1:<port>, even though the normalized user-visible URL should stay on localhost.

Impact

Users opening a discovered localhost dev server from a local prepared environment keep the localhost host, which preserves host-specific API allowlists. Wildcard local hosts such as 0.0.0.0 still normalize to a concrete reachable host, and private remote environments still remap discovered loopback ports onto the private environment host.

Validation

• PATH="$HOME/.vite-plus/bin:$PATH" vp test apps/web/src/browser/browserTargetResolver.test.ts
• PATH="$HOME/.vite-plus/bin:$PATH" vp check
• PATH="$HOME/.vite-plus/bin:$PATH" vp run typecheck

vp check reports the repository's existing lint warnings and no errors.

Closes pingdotgg#3124