Improve tracebacks, network builtins, and VM parity

[orderofdan]

Improve runtime error reporting across the VM, scheduler, eval(), and builtins so failures preserve useful messages instead of collapsing into generic type/args output. Add builtin signature-based enrichment for bare E_ARGS/E_TYPE failures, carry explicit messages through traceback formatting, and make eval() return Toast-style traceback line lists with better call boundary reporting.

Implement missing network/listener behavior so compatibility builtins use the real connection manager instead of placeholder state. listen(), unlisten(), listeners(), open_network_connection(), flush_input(), held input replay, client-echo telnet negotiation, binary/raw notify output, and keep-alive now operate through server connection plumbing and transport support.

Close several VM/tree-walker parity gaps. Fix scatter optional bindings to assign 0 instead of leaving variables unbound, restore except e (...) binding to error codes, deep-copy waifs into fork snapshots, preserve line-aware exception messages, and align toint() / truthiness behavior with current test expectations.

Tighten permission enforcement for object, property, and verb mutators. Require owner/wizard checks for verb and property mutations, enforce fertile-parent checks for chparent/chparents, and restore wizard-only behavior for renumber.

Add focused regression coverage for traceback messaging, network option side effects, listener/open connection behavior, sort() parameter handling, waif deep-copy behavior, permission checks, scheduler message normalization, and eval() runtime error contracts. Also clean up repo test/build hygiene so go test ./... passes without scratch binaries or fixture-path issues breaking the run.