feat: migrate codegen to LLVM 22

[baszalmstra]

Why

LLVM 14's typed pointers encode pointee meaning in pointer types. LLVM 22 is the newest release supported by Inkwell 0.10 and uses opaque pointers, so Mun must carry load, GEP, and indirect-call types explicitly in its own codegen model.

What

• move the Pixi toolchain to LLVM/LLD 22 and Inkwell 0.10
• provide explicit types for loads, projections, and indirect calls
• use LLVM's module pass pipeline
• refresh IR snapshots for opaque ptr and LLVM 22 GEP flags

Depends on mun-lang/lld-rs#10.

Testing

• pixi run check with RUSTFLAGS=-Dwarnings
• pixi run clippy with RUSTFLAGS=-Dwarnings
• pixi run cargo test -p mun_codegen --lib
• pixi run cargo test -p mun_codegen --test abi
• targeted runtime dispatch, array, and hot-reload tests

[codecov]

Codecov Report

❌ Patch coverage is 98.17629% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 87.56%. Comparing base (55f1c13) to head (c0d86a3).

Files with missing lines	Patch %	Lines
crates/mun_codegen/src/ir.rs	66.66%	2 Missing ⚠️
crates/mun_codegen/src/ir/body.rs	98.99%	2 Missing ⚠️
crates/mun_codegen/src/code_gen.rs	92.30%	1 Missing ⚠️
crates/mun_codegen/src/ir/types.rs	93.75%	1 Missing ⚠️

Additional details and impacted files

@@                   Coverage Diff                   @@
##           bas/typed-callables     #608      +/-   ##
=======================================================
+ Coverage                87.46%   87.56%   +0.10%     
=======================================================
  Files                      254      254              
  Lines                    26946    27050     +104     
=======================================================
+ Hits                     23567    23687     +120     
+ Misses                    3379     3363      -16     

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