Uniform/canonical Result layout so composite payloads pass through generic Result params (M4)

[assapir]

Give Result a single uniform/canonical LLVM layout so a value of any payload type can pass through a generic (r :: Result) parameter or return.

Problem

A generic (r :: Result) param currently lowers to {i8, double} (discriminant + f64 payload slot), but a composite-payload Result is {i8, {ptr, i64}} (e.g. Ok(Text), Ok([]Text)). LLVM rejects the call because the aggregate types don't match. Result deliberately has no canonical sum_layouts entry today — its shape follows the concrete payload — so any function taking a bare Result can only accept discriminant-compatible (f64-payload) values.

This blocks core.test's assertOk/assertNotOk (and any user helper) from operating on a Result carrying a composite payload. Surfaced by core.cli (getEnv → Ok(Text), getOpt → Ok([]Text)): the self-asserting example must verify presence via match → Bool + assert(...) instead of assertOk/assertNotOk.

Decision (LOCKED)

Full uniform/canonical Result representation — a single layout that construction, every ?/| match, and all Result params/returns agree on, so any payload passes through a generic Result. Chosen over a narrow discriminant-only call-site coercion (a band-aid that wouldn't let the payload be used through a generic Result).

Scope

Part of M4 (monomorphization + authoritative types in codegen). Cross-cutting: touches Result construction, matching/extraction, and Result-typed params/returns. Not a blocker for core.cli (#66) — that ships with the match → Bool + assert workaround.

Unblocks

• assertOk/assertNotOk on composite-payload Results everywhere (convert the core.cli example off the match → Bool workaround).
• General use of composite-payload Result values through generic Result params/returns.