Expose duplicate no-mutation evidence from the generic runner

[flyingrobots]

Claim

The generic compiler-produced operation runner refuses a duplicate path that mutates committed application state, but its JSON witness exposes only the typed obstruction. Expose independently comparable before/after evidence produced from Echo's authoritative application state without adding application vocabulary.

Executable witness

cargo test -p xtask --test run_edict_operation

Acceptance criteria

• duplicate reports canonical before/after application-state roots computed from Echo's graph-only state root, excluding WAL, history, Receipt, and commit metadata.
• duplicate reports before/after target-value digests so the claimed target value is independently bound even if root coverage changes later.
• The success witness requires both root and target-value pairs to match.
• A negative runner test proves a root or target-value change cannot produce a passing report.
• The existing fail-closed hidden-mutation check remains on the production path.
• Generic production code contains no Hello Echo application vocabulary.

Consumer

Blocks flyingrobots/hello-echo#4 and remediation of flyingrobots/hello-echo#17 review thread PRRT_kwDOTmLBK86UkvoG.

Non-goals

• Application-specific reconstruction.
• Result-projection work tracked separately by Evaluate package-declared typed application results #698.
• Any change to the compiler/provider authority boundary.

[coderabbitai]

🔗 Related PRs

#683 - Execute admitted data-only operations in Echo [merged]
#686 - feat(warp-core): add anchored-node create-if-absent program [merged]
#688 - Route executable-operation Actions through scheduler-owned Ticks [merged]
#695 - Run compiler-produced Edict operations through durable Ticks [open]
#697 - Preserve typed executable-operation obstructions [open]

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