[pyrex41]

Why

The Rust target for pyrex41/yggdrasil#29 could not reach the model-checker fixture: yggdrasil-build on current shen-rust main failed to compile because its CompileOptions initializer omitted seal_same_module. After that was supplied, the builder refused Yggdrasil's manifest v4.

Change

• Set seal_same_module: false for generated external modules, matching CompileOptions::external and preserving runtime rebinding.
• Accept manifest v3 and v4. The parser already ignores unknown keys and reads the same kernel, init, user, and fn fields from both.

Verification

• cargo build --release -p yggdrasil-build passed.
• From Yggdrasil PR Update to Shen kernel 43.1 (S43) #30 at 8718c8c, scripts/parity-gate.sh --fixtures tla-election --targets rust --min-targets 1 passed: build, golden comparison, and two-boot comparison.

This unblocks the Rust target check for pyrex41/yggdrasil#29; it does not implement the separate native visited-map optimization.