Troubleshoot backend module builds and runtime failures

Identify the stage

• Source or compiler error: fix the first actionable diagnostic and rebuild.
• Dependency unavailable: use dependencies supported by the managed offline toolchain; builds cannot download arbitrary packages.
• Wasm or ABI validation failure: confirm the supported language scaffold, WASI Preview 1 target, and blinkhost-wasi-1 contract.
• Artifact rejected: preserve the build ID and validation diagnostic; a compiler exit code alone does not make an artifact deployable.
• Runtime capability denied: inspect the effective signed runtime policy and named binding rather than embedding credentials.
• Runtime trap, timeout, or memory limit: reproduce with bounded input and review logs for the exact release and module artifact.

If source and toolchain identity are unchanged, BlinkHost can reuse an already verified artifact. Select a previous healthy artifact to recover; do not rebuild old source as a rollback. Python remains Production Preview, so verify package compatibility, cold start, and memory behavior before assuming parity with a conventional Linux Python service.