test(reborn): cover WASM runtime failure edges

[serrrfirat]

Summary

Test-only follow-up for #3086 to close the remaining explicit WASM runtime coverage gaps after #3097 and #3109 landed.

Adds coverage for:

• malformed non-WASM bytes rejected by WitToolRuntime::prepare
• valid core WASM module bytes rejected because they are not component-model tools
• component-model inputs without the required WIT tool exports
• invalid WIT schema exports that are not JSON objects
• missing WASM module files through the RuntimeDispatcher / RuntimeAdapter seam
• malformed module bytes through the dispatch seam as sanitized manifest errors
• invalid output JSON through the dispatch seam as sanitized output decode errors

No production code changes.

Verification

cargo fmt --all -- --check
CARGO_TARGET_DIR=/tmp/ironclaw-reborn-wasm-coverage-target cargo test -p ironclaw_wasm
CARGO_TARGET_DIR=/tmp/ironclaw-reborn-wasm-coverage-target cargo clippy -q -p ironclaw_wasm --all-targets -- -D warnings
CARGO_TARGET_DIR=/tmp/ironclaw-reborn-wasm-coverage-target cargo test -p ironclaw_architecture
CARGO_TARGET_DIR=/tmp/ironclaw-reborn-wasm-coverage-target cargo test -p ironclaw_dispatcher
git diff --check

Links

Completes #3086.
Part of #2987.

[gemini-code-assist]

Code Review

This pull request introduces several integration and unit tests to verify error handling and sanitization for WASM module dispatching and runtime preparation. Specifically, it covers scenarios such as missing module files, malformed modules, invalid output JSON, and unsupported component exports. I have no feedback to provide.