Policies with allowed_ips entries targeting loopback, link-local, or
unspecified ranges now fail at connection time instead of being silently
blocked at runtime. The shorthand log format for DENIED events includes
a [reason:...] suffix so operators can distinguish 'allowlist miss' from
'structurally un-allowable'. The mechanistic mapper skips proposals for
always-blocked destinations, preventing the infinite TUI notification
loop. The gateway validates proposed rules on approval as defense-in-depth.
- Extract shared IP helpers (is_always_blocked_ip, is_always_blocked_net,
is_internal_ip) to openshell_core::net
- Reject always-blocked entries in parse_allowed_ips with hard error
- Skip implicit allowed_ips synthesis for always-blocked literal IP hosts
- Add status_detail to HttpActivityBuilder for denial reason propagation
- Enrich NET and HTTP shorthand with [reason:...] for DENIED events
- Add engine: tag to HTTP shorthand (consistency with NET shorthand)
- Filter always-blocked proposals in mechanistic mapper generate_proposals
- Add validate_rule_not_always_blocked server-side defense-in-depth
- Update architecture docs, published docs, and E2E test assertions
John T. Myers