Pre-build spec for the uniform cross-harness capture path. Grounds the design in the homelab invariants (I1-I5, now canonical on infra main): - I1 sovereignty gate: refuse confidential capture via us-nexus harness - I2: distributed-library form (no high-degree observer node) is admissible; central relay needs a security-baseline ledger entry - I5: capture is a privileged write path, must emit audit records Gherkin scenarios cover the happy path, the sovereignty refusal, supersession + staleness discipline (#45/#47), fail-closed validation, best-effort partial-failure receipts, dry-run, and fidelity supersession. Four open questions flagged for review (classification trust is the highest-risk one).