docs: add record of legacy retractions and spikes

Author: hyperpolymath

docs/retracted/legacy-retractions.md

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+# Legacy Retractions and Spikes
+
+This document records exploratory branches that were discarded or retracted as part of the refactoring into a minimal defensible core. These branches exist on GitHub for historical reference but have been removed from the local workspace to maintain structural integrity.
+
+## Retracted Theory Branches
+- `f1-spike/graded-comonad-checkpoint`: Exploratory work on the "Graded Comonad" framing. Retracted on 2026-05-18 after finding the structure is a thin-poset action, not a true graded comonad.
+- `reframe/retraction-2026-05-18`: Initial draft of the 2026-05-18 reframing and retraction logic.
+
+## Abandoned Spikes
+- `f3-interface-phase1`: Superseded by the Axis 8 (Access Modality) and established core interfaces.
+- `roadmap/proof-debt-ledger-2026-05-18`: Superseded by the `docs/proof-obligations.md` ledger.