Reproduce stale circuit JSON after a failed rebuild

[ShiboSoftwareDev]

Reproduction

This adds a focused integration test that:

1. successfully builds index.tsx and saves dist/index/circuit.json
2. replaces the same source file with a component that throws during circuit generation
3. runs the same build again and confirms the command exits with a fatal error
4. records that the previous circuit.json is still present byte-for-byte

The stale artifact can therefore look like the failed source revision built successfully to downstream fabrication or inspection tooling.

Expected behavior

A failed rebuild must not leave the prior circuit.json at the output path for that entrypoint.

Actual behavior

The fatal build exits 1, but dist/index/circuit.json still contains the previous successful build.

Test

• bun test tests/cli/build/build-failed-rebuild-stale-output.test.ts
• bun run format:check

This is the reproduction PR. The fix is intentionally kept in the next PR in the stack.

[github-actions]

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