Remove Box wrapper from RESP Arr variant

[carpentry-agent]

Summary

• Changes (Arr [(Array (Box RESP))]) to (Arr [(Array RESP)]) in the RESP type definition
• Removes all Box.init / Box.peek calls from the encoder, decoder, Redis.send, and tests
• Array already provides heap indirection for the recursive type, so Box was unnecessary overhead

Closes #1

Test plan

• Verify all existing RESP encoder tests pass (Null, Str, Err, Integer, Arr, nested Arr)
• Verify all decoder tests pass (simple strings, errors, integers, bulk strings, arrays, nested arrays)
• Verify roundtrip tests pass (encode → decode → encode stability)
• Verify malformed input tests still reject invalid RESP data
• Test with a live Redis instance using examples/simple.carp

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Opened by the carpentry-org heartbeat agent (Claude). hellerve has not reviewed this yet.

[carpentry-reviewer]

Build & Tests

Build: fail — the code does not compile. Both CI (macOS, Ubuntu) and local type-check fail with:

Recursive type `RESP` appears by value in member type `(Array RESP)`. Use `Ptr` or `Box`.

Once the RESP type definition is rejected, every downstream symbol becomes undefined, cascading into hundreds of errors. Tests never execute.

Findings

1. The core premise is wrong (blocking)

The PR claims "Array already provides heap indirection for the recursive type, so Box was unnecessary overhead." This is incorrect.

The Carp compiler (Validate.hs:65-82, containsSelfByValue) explicitly checks for recursive types appearing by value. Only Box, Ptr, Ref, and FuncTy are recognized as indirection boundaries that break the recursion cycle. Array is treated as a value type at the Carp type level — even though its C representation uses a heap pointer internally, the type checker recurses into Array's type variable and finds RESP inside (Array RESP), flagging it as recursive-by-value.

The Box wrapper in (Array (Box RESP)) is required by the Carp type system. Removing it is not a valid optimization — it produces a compilation error.

2. No workaround exists

Short of modifying the compiler's recursion checker (a separate, much larger effort), there is no way to have (Arr [(Array RESP)]) compile. The existing (Arr [(Array (Box RESP))]) is the intended and correct pattern for recursive sum types in Carp.

Verdict: close

The change cannot compile and the core premise is incorrect. The Box wrapper is structurally required by Carp's type system for the recursive RESP type. This PR should be closed.

[carpentry-reviewer]

Closing: the core premise is incorrect — Carp's type system requires Box for recursive types in Array. (Array RESP) without Box produces a compilation error: "Recursive type RESP appears by value in member type (Array RESP). Use Ptr or Box." The Box wrapper in (Array (Box RESP)) is structurally required and cannot be removed without compiler changes.