Deno -g misses a one-segment path registry behind a same-named cached package #1784

[agent] Follow-up to #1719 (merged at 40ef0c1 with this unaddressed; review comment).

Scenario: one host serves an npm registry at its root (https://host/) and another one path segment below it (https://host/npm/), and the root registry has cached a package named like that segment (npm). Deno puts both under $DENO_DIR/npm/host/, so host/npm/ holds the root registry's package npm (host/npm/10.9.0/) and the nested registry's packages (host/npm/foo/1.0.0/).

Actual: in deno_npm_registry_dirs (crates/socket-patch-core/src/crawlers/npm_crawler.rs, the if is_deno_package_dir(&child) branch, ~line 1953 on main), host/npm counts as a package dir, so only its non-version subdirs (host/npm/foo) are queued. holds_deno_packages(host/npm/foo) is false, since its children are version dirs with a package.json, so host/npm never becomes a root. -g scan and apply report the https://host/npm/ registry's packages as not installed and leave them unpatched, with no warning.

Expected: both host and host/npm are registry roots.

Fix: when a child is a package dir, also check its non-version subdirs with holds_deno_packages (ignoring digit-named dirs). If they hold packages, push the child itself as a registry root, the same as the non-package branch does. global_mode_finds_one_segment_registry_under_root_registry doesn't cache a package npm at the host root, so a test needs that added.