[codex] link net validation helpers in no-auto parity

[andrewtdiz]

Refs #2013.

Summary

• Route net validation helper FFIs (getDefaultAutoSelectFamily* and socket.setTimeout) through the codegen FFI provider registry so native-table emissions pull in perry-ext-net.
• Teach the parity runner to prebuild perry-ext-net for node-suite/net selections, so PERRY_NO_AUTO_OPTIMIZE=1 has the well-known archive available on clean worktrees.
• Add an ext_registry regression test covering the net validation symbols plus existing create/listen rows.

Verification

• bash -n run_parity_tests.sh
• cargo test -p perry-codegen ext_registry::tests::emitted_net_validation_external_symbols_route_to_net -- --nocapture
• PATH="/root/.npm/_npx/bac97da9607b7ef2/node_modules/node/bin:$PATH" PERRY_NO_AUTO_OPTIMIZE=1 ./run_parity_tests.sh --suite node-suite --module net --filter validation
• cargo fmt --all -- --check
• git diff --check
• ./scripts/check_file_size.sh
• cargo check -p perry-codegen -p perry
• cargo test -p perry-codegen ext_registry::tests -- --nocapture