refactor: strip no_std from kiln-runtime — std-only interpreter per RFC #46

[avrabe]

Summary

• RFC build(deps): bump wast from 228.0.0 to 229.0.0 #46 architecture docs: toolchain architecture, interface design, C API reference for the std-only interpreter / kiln-builtins split
• Phase 1: Strip no_std from prelude.rs and lib.rs — remove 414 lines of cfg-gated polyfills, bounded collections, custom macros
• Phase 2: Strip no_std from all 30 remaining source files — remove 1,251 lines of dead #[cfg(not(feature = "std"))] code paths, simplify compound guards (cfg(all(std, debugger)) → cfg(debugger))

Result: Zero cfg(feature = "std") / cfg(not(feature = "std")) guards remain in kiln-runtime. The interpreter is fully std-only. The no_std path is via kiln-builtins for synth-compiled code targeting gale/Zephyr.

Test plan

• cargo check -p kiln-runtime — clean compile
• cargo test -p kiln-runtime --lib — 95/95 tests pass
• CI passes

🤖 Generated with Claude Code

[github-actions]

🔍 Build Diagnostics Report

Summary

Metric	Base Branch	This PR	Change
Errors	0	0	0
Warnings	2	2	0

🎯 Impact Analysis

Issues in Files You Modified

• 0 new errors introduced by your changes
• 0 new warnings introduced by your changes
• 0 total errors in modified files
• 0 total warnings in modified files
• 0 files you modified

Cascading Issues (Your Changes Breaking Other Files)

• 0 new errors in unchanged files
• 0 new warnings in unchanged files
• 0 unchanged files now affected

Note: "Cascading issues" are errors in files you didn't modify, caused by your changes (e.g., breaking API changes, dependency issues).

✅ No Issues Detected

Perfect! Your changes don't introduce any new errors or warnings, and don't break any existing code.

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🔧 To reproduce locally:

# Install cargo-kiln
cargo install --path cargo-kiln

# Analyze your changes
cargo-kiln build --output json --filter-severity error
cargo-kiln check --output json --filter-severity warning