fix(wasm): arm epoch deadline before instantiation

[qciaran]

Summary

• Arm the Wasmtime epoch deadline before Instance::new so module start functions receive the configured timeout.
• Add a Rust regression test covering initial construction and init-time re-instantiation with a tracked WAT fixture.
• Exercise the same WAT fixture through the built pecos-rslib wheel in the Python compatibility matrix, including macOS arm64.

Context

With Wasmtime 46 on macOS arm64, the epoch thread can advance while a sufficiently complex module is being instantiated. The store previously kept Wasmtime's default epoch deadline until exec armed it for an exported call, so Instance::new could trap with interrupt before execution began.

This PR arms the existing timeout deadline for every instance creation. It intentionally tracks only the textual WAT regression fixture; no WASM binary is added.

Validation

• cargo test -p pecos-wasm
• cargo clippy -p pecos-wasm --all-targets -- -D warnings
• cargo fmt --all --check
• uv run ruff check scripts/ci/smoke_wasm_foreign_object.py
• uv run ruff format --check scripts/ci/smoke_wasm_foreign_object.py
• qemulator targeted WASM tests: 6 passed
• qemulator full suite against an optimized patched pecos-rslib: 199 passed, 3 skipped