All arbitrary Lab code segments must target WebAssembly. Implement lab.run/1 with explicit capability profiles, fresh isolated execution by default, bounded CPU/memory/output/time, no network by default, read-only declared inputs, and a scratch output directory. Avoid a hidden mutable Jupyter kernel as the canonical execution model.

Acceptance: - At least one compiled code cell runs in the browser or server WASM runtime and emits streamed events plus artifacts. - Default execution has no host filesystem, process, credential, or network access. - Capability escalation is explicit, reviewable, and recorded in the run ledger. - Runs are reproducible from source/check-in, module/toolchain digest, declared inputs, and parameters. - Timeout, out-of-memory, output-flood, and invalid-module cases fail safely. - A kill switch disables execution without disabling pure rendering.