feat: kiln-builtins crate — no_std staticlib for synth-compiled embedded targets

[avrabe]

Summary

Phase 1 stub of kiln-builtins per RFC #46 toolchain architecture. This is the C ABI bridge between synth-compiled ARM ELF binaries and kiln's runtime services.

Functions

• __meld_dispatch_import(import_index: u32) -> u32 — stub, returns 0
• __meld_get_memory_base() -> *mut u8 — returns linker-provided memory base
• cabi_realloc(old_ptr, old_size, align, new_size) -> u32 — bump allocator
• __kiln_builtins_init(heap_start: u32) — initialize bump allocator

Build

cargo build -p kiln-builtins --target thumbv7em-none-eabi --release
# Produces: target/thumbv7em-none-eabi/release/libkiln_builtins.a

Properties

• Pure no_std, zero dependencies
• Builds as staticlib for ARM Cortex-M4
• Enables synth --link --builtins integration
• Phase 2: real WASI dispatch via import table from meld

[github-actions]

🔍 Build Diagnostics Report

Summary

Metric	Base Branch	This PR	Change
Errors	0	0	0
Warnings	5	8	3

🎯 Impact Analysis

Issues in Files You Modified

• 0 new errors introduced by your changes
• 3 new warnings introduced by your changes
• 0 total errors in modified files
• 3 total warnings in modified files
• 1 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).

⚠️ Warnings in Modified Files

kiln-builtins/src/lib.rs:400:7 - unexpected cfg condition name: kani (unexpected_cfgs)
kiln-builtins/src/lib.rs:182:5 - unnecessary unsafe block (unused_unsafe)
kiln-builtins/src/lib.rs:249:4 - function platform is never used (dead_code)

✅ No Cascading Issues

Good! Your changes don't break any existing code in other files.

---

📊 Full diagnostic data available in workflow artifacts

🔧 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