Add brokered IPv4 TCP clients

[wdcui]

This PR wires IPv4 TCP client sockets through the broker-owned Linux reactor while keeping descriptor flags, blocking behavior, timeouts, polling, and waiters local to LiteBox. It adds operation-scoped shared-buffer transfers and Linux-compatible connect, error, half-close, readiness, MSG_TRUNC, MSG_PEEK, and MSG_WAITALL behavior, plus authoritative names and socket errors. It also adds syscall-rewriter loopback coverage for nonblocking and blocking I/O, large split receives, backpressure, poll/epoll, shutdown, policy failures, resets, and partial-copy faults.

[github-actions]

🤖 SemverChecks 🤖 ⚠️ Potential breaking API changes detected ⚠️

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--- failure enum_discriminants_undefined_non_unit_variant: enum's variants no longer have defined discriminants due to non-unit variant ---

Description:
An enum's variants no longer have well-defined discriminant values due to a tuple or struct variant in the enum. This breaks downstream code that accesses discriminants via a numeric cast like `as isize`.
        ref: https://doc.rust-lang.org/reference/items/enumerations.html#assigning-discriminant-values
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.50.0/src/lints/enum_discriminants_undefined_non_unit_variant.ron

Failed in:
  enum ChannelReadError in /home/runner/work/litebox/litebox/litebox/src/net/socket_channel.rs:136
  enum ChannelWriteError in /home/runner/work/litebox/litebox/litebox/src/net/socket_channel.rs:151

--- failure enum_variant_added: enum variant added on exhaustive enum ---

Description:
A publicly-visible enum without #[non_exhaustive] has a new variant.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#enum-variant-new
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.50.0/src/lints/enum_variant_added.ron

Failed in:
  variant ChannelWriteError:Socket in /home/runner/work/litebox/litebox/litebox/src/net/socket_channel.rs:165
  variant NetworkProxy:BrokerStream in /home/runner/work/litebox/litebox/litebox/src/net/socket_channel.rs:194
  variant ChannelReadError:WouldBlock in /home/runner/work/litebox/litebox/litebox/src/net/socket_channel.rs:140
  variant ChannelReadError:Socket in /home/runner/work/litebox/litebox/litebox/src/net/socket_channel.rs:146

--- failure inherent_method_missing: pub method removed or renamed ---

Description:
A publicly-visible method or associated fn is no longer available under its prior name. It may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.50.0/src/lints/inherent_method_missing.ron

Failed in:
  Network::set_socket_proxy, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/c0985945b9dd77f3028594f4ba499a9379f1a234/litebox/src/net/mod.rs:814

--- failure enum_missing: pub enum removed or renamed ---

Description:
A publicly-visible enum cannot be imported by its prior path. A `pub use` may have been removed, or the enum itself may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.50.0/src/lints/enum_missing.ron

Failed in:
  enum litebox_broker_core::socket::SocketOutcome, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/c0985945b9dd77f3028594f4ba499a9379f1a234/litebox_broker_core/src/socket.rs:24

--- failure function_parameter_count_changed: pub fn parameter count changed ---

Description:
A publicly-visible function now takes a different number of parameters.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#fn-change-arity
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.50.0/src/lints/function_parameter_count_changed.ron

Failed in:
  litebox_broker_core::socket::receive now takes 6 parameters instead of 4, in /home/runner/work/litebox/litebox/litebox_broker_core/src/socket.rs:228

--- failure trait_method_parameter_count_changed: pub trait method parameter count changed ---

Description:
A trait method now takes a different number of parameters.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#trait-item-signature
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.50.0/src/lints/trait_method_parameter_count_changed.ron

Failed in:
  PlatformSocket::receive now takes 4 instead of 2 parameters, in file /home/runner/work/litebox/litebox/litebox_broker_core/src/socket.rs:68

--- failure constructible_struct_adds_field: struct exhaustively constructible through public API adds field ---

Description:
A pub struct that could be exhaustively constructed with a literal using only public API has a new pub field, breaking existing exhaustive literals.
        ref: https://doc.rust-lang.org/reference/expressions/struct-expr.html
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.50.0/src/lints/constructible_struct_adds_field.ron

Failed in:
  field SocketStatusResponse.local_address in /home/runner/work/litebox/litebox/litebox_broker_protocol/src/socket.rs:368
  field SocketStatusResponse.pending_error in /home/runner/work/litebox/litebox/litebox_broker_protocol/src/socket.rs:370
  field ReceiveSocketRequest.peek_offset in /home/runner/work/litebox/litebox/litebox_broker_protocol/src/socket.rs:326
  field ReceiveSocketRequest.peek_length in /home/runner/work/litebox/litebox/litebox_broker_protocol/src/socket.rs:328