Bootstrap project and safe work-item workflow

delivery_backlog/stories/US01-04-duplicate-engine.md

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+# US01-04 — Detect and Decide Duplicates
+
+Epic: [E01](../E01-shared-identity-inventory.md)
+
+As a user, I want explainable duplicate clusters and reversible decisions so redundant
+copies are excluded without collapsing distinct photos automatically.
+
+## Acceptance criteria
+
+- Donor exact, normalized-pixel, and perceptual hash behavior is extracted and
+  versioned.
+- Confidence bands distinguish automatic exact matches from fuzzy review candidates.
+- Canonical, variant, not-duplicate, and deferred decisions persist with evidence.
+- New contradictory members reopen reviewed clusters; canonical links cannot cycle.
+
+## Automated tests
+
+- Golden corpus tests assert hash relationships and confidence classes.
+- Property/integration tests cover clustering, negative links, reversals, new members,
+  and persistence after restart.
+
+## Dependencies
+
+- US01-03