L04-03 — Compute isolated nonpublishing preview #35

Outcome

Produce technical and visual preview from immutable input/plan with candidate identity and fidelity mode.

Parent and boundary

Parent: #5. Owner: LoopLibCore correction subsystem. This issue owns one bounded slice of Governed Operation Engine; consume accepted upstream contracts and keep PDF/verdict/publication authority with Core.

Acceptance

• Preview exposes intended and unexpected changes without publishing or modifying source.
• Failure case: Cancelling or failing preview leaves no externally visible artifact or approval.

Required proof

Byte-level source immutability and crash/cancel tests. Record the exact source SHA, test command or hosted run, fixture/artifact identity, and any skipped or unavailable lane. Run the repository's mapped proof and check-change gate for a PR.

Handoff

Record changed files, observed result, remaining risk, and a 1–3 sentence anti-slop review. Completion means acceptance evidence, not merely a merged implementation.

Sources

Approved master roadmap · Legacy/research input (legacy #586).