Support static field byte[] arrays in ldelem.u1

[Copilot]

Thanks for assigning this issue to me. I'm starting to work on it and will keep this PR's description up to date as I form a plan and make progress.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Transpiler: HandleLdelemU1 requires array in tracked local variable</issue_title>
<issue_description>## Problem

The transpiler's HandleLdelemU1ComplexIndex throws when the array being accessed is not stored in a tracked local variable. The error occurs during transpilation of the crypto sample after closure inlining.

TranspileException: Array element access requires the array to be stored in a local variable.
   at IL2NESWriter.HandleLdelemU1ComplexIndex() in IL2NESWriter.ArrayHandling.cs:line 530
   at IL2NESWriter.HandleLdelemU1() in IL2NESWriter.ArrayHandling.cs:line 368

Expected behavior

The transpiler should handle ldelem.u1 when the array reference comes from patterns other than a simple ldloc, such as when the compiler reuses a register or optimizes array access in inlined code.

Context

• Blocking: crypto sample (PR Port 8bitworkshop crypto.c dungeon crawler sample #211)
• This error surfaced after inlining all local functions to eliminate closure captures
• The inlined code produces IL patterns where array references may not follow the expected ldloc+ldloc+ldelem sequence
  </issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Transpiler: HandleLdelemU1 requires array in tracked local variable #273

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[jonathanpeppers]

🤖 Took over from CCA. CI is green, all 527 tests pass.

What this fixes

When byte[] arrays are stored as static fields in static class G, the IL uses ldsfld to load the array reference before ldelem.u1. The transpiler only checked GetLdlocIndex(), missing static field arrays entirely.

Changes

Transpiler (allocation):

• Scan .cctor (static constructor) for newarr → stsfld patterns to determine array sizes
• Detect ELEMENT_TYPE_SZARRAY (0x1D) in field signatures to identify array fields
• PreAllocateStaticFields now allocates proper byte counts for array fields and returns array metadata

IL2NESWriter (code generation):

• TryResolveArrayLocal() helper resolves arrays from both ldloc and ldsfld sources
• HandleLdelemU1: falls back to static field array lookup when GetLdlocIndex returns null
• HandleLdelemU1ComplexIndex: same ldsfld fallback
• HandleLdelemU1: resolves indices from ldsfld (static field scalars like G.i)
• ILDispatch: handles newarr → stsfld to track runtime array allocations

Verified with crypto sample

The crypto sample (PR #211) now progresses past this error. The next blocker is ldelema for byte arrays (a separate issue).

[Copilot]

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