[Cloudflare One] Add package protection documentation

[grstnhbr]

What this PR does

Adds public-facing documentation for Gateway package protection, a new feature that detects and filters software package downloads across seven major package ecosystems (npm, PyPI, RubyGems, Cargo, Go, Maven, NuGet).

Changes

New page: traffic-policies/http-policies/package-protection.mdx

• How detection works (URL path structure, not hostname-based)
• Supported ecosystems table with artifact patterns and namespace details
• pkg.* selector reference (pkg.ecosystem, pkg.name, pkg.version, pkg.namespace, pkg.purl)
• Version comparison operators with ecosystem-aware ordering (SemVer, PEP 440, Maven, Go, NuGet, RubyGems)
• Five example policies covering common use cases:
  • Block an entire ecosystem
  • Block a specific package
  • Block vulnerable versions (version comparison)
  • Restrict packages to a sanctioned registry mirror
  • Block a specific package unless from a sanctioned host
• Mirror and proxy registry detection explanation
• Logging section (Activity Log and Logpush fields)
• Limitations

Modified: http-policies/index.mdx

• Added five new selector entries (Package Ecosystem, Package Name, Package Namespace, Package URL, Package Version) to the selectors reference section

Modified: partials/cloudflare-one/gateway/http-allow-block-selectors.mdx

• Added the five pkg.* selectors to the Allow/Block action availability lists

Not included (requires separate work)

• Logpush dataset update: The gateway_http.md Logpush dataset page is code-generated (DO NOT EDIT). The PackageInfo object needs to be added to the upstream schema/code generator that produces this file.

Related

• Functional spec: https://wiki.cfdata.org/spaces/GATE/pages/1419350587/Functional+Spec+Package+Protection
• SHIP-15299 / RM-29835
• Key MRs: GRE !979, !980, !1001, !1010, !1015 | oxy-teams !3754, !3810 | ARAS !3565, !3604 | ztx-frontend !11120