Internal @tcpRequest socket primitive: deferred-Text request exchange (#143)

[assapir]

What

Adds the low-level socket @ primitive the HTTP client (#143) will sit on:

@tcpRequest(address :: Text, requestBytes :: Text) -> Text   ~ deferred

A one-shot, close-delimited TCP request exchange — connect to address (host:port), write the request bytes, read the response until the peer closes — returning all response bytes as a deferred Text, forced on use exactly like @readStdin. This is design (a): the deferred value is raw response bytes; HTTP framing/parsing will happen in Quilon on force.

How it fits the existing model

• Reuses, does not rebuild: it is a launch(|| ...) producer over the merged reactor-parked non-blocking TCP (quilon-rt/net.rs) and the generic launch/Deferred/force core (Deferred values + @readStdin: the value-returning half of colorless implicit futures #149). No new park/deferred plumbing.
• A new launch_deferred_text wrapper now holds the { deferred, -1 } C-ABI tagging in one place, shared by both value-returning primitives (@readStdin, @tcpRequest).
• The producer copies its address/request into owned buffers before the background fiber is spawned, so it never reads a caller Text that a later collection could reclaim.
• The existing force machinery (__force_text, the deferred-taint pass) works unchanged — @tcpRequest is just recognized as a second deferred-producing primitive.

Sockets stay internal

Declared in a new trusted, internal corelib module internal.net (added to the @-declaration gate CORELIB_SOURCES), not a public core.net. The HTTP client imports it; users do not import raw sockets. No public corelib doc (it is not user-facing); noted in LANGUAGE.md's concurrency / @-primitives section as an internal primitive.

Fault handling

Fail-loud on resolve/connect/write/read failure, reporting the target address and the stage it failed at, then __exit(1) — same posture as the stdin reader.

Tests

• Runtime round-trip (quilon-rt/net.rs): launch @tcpRequest against a local std::net listener on its own thread, force the deferred value on a fiber, assert the response bytes.
• Compiler JIT + AOT round-trip (tests/tcp_request_test.rs): spawn a local listener, compile+run a .ql program that does one @tcpRequest and assertEqs the response — matching response exits 0, a wrong expectation trips the assertion (proving the real server bytes flowed and forced), under both quilon run (JIT) and quilon build (native AOT).
• Extends the intrinsic-link smoke gate to cover __tcp_request_launch (guarded by a runtime-false branch so the symbol is emitted but no real connection runs).
• Deferral-taint unit tests mirror the @readStdin ones.

Full suite passes; cargo fmt --check + clippy -D warnings clean. Reviewed via read-only correctness and simplification passes (no bugs; one duplication consolidated into launch_deferred_text).

Status

PARKED — do not merge without explicit per-PR approval.

Known limitation (documented): to_socket_addrs DNS resolution for a hostname is blocking; numeric addresses (the tests) never block. Non-blocking DNS is a later refinement.

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