Formalize headline theorem from Knuth's "Claude's Cycles" paper

Prove that for odd m > 1, each of Claude's three cycles is a directed
Hamiltonian cycle on the cube digraph (ZMod m)³. The proof follows
Knuth's fiber-based trajectory argument with return map analysis for
each cycle.

Remaining sorry's are in optional Phase 4 theorems (counting results,
generalizability, symmetry) independent of the headline.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: kim-em

.github/workflows/lean_action_ci.yml

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+name: Lean Action CI
+
+on:
+  push:
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v5
+      - uses: leanprover/lean-action@v1

.gitignore

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+/.lake

KnuthClaudeLean.lean

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+-- This module serves as the root of the `KnuthClaudeLean` library.
+-- Import modules here that should be built as part of the library.
+import KnuthClaudeLean.Basic