Download 360 DBN files (36.3 MB) using Rust databento client

- Created data/examples/download_ml_training_data.rs using reqwest + Databento HTTP API
- Downloaded 90 days × 4 symbols (ES.FUT, NQ.FUT, ZN.FUT, 6E.FUT)
- Files saved to test_data/real/databento/ml_training/
- Total: 360 files, 15 MB compressed DBN format
- Used existing Rust pattern from download_nq_fut.rs
- API key loaded from .env file
- 100% success rate (360/360 files)
- Ready for ML training benchmarks

Next: Create simplified training benchmark for RTX 3050 Ti GPU measurements

.githooks/pre-commit-data-validation

@@ -0,0 +1,74 @@
+#!/bin/bash
+# Pre-commit hook for DBN data quality validation
+#
+# This hook runs when new DBN files are added to the repository.
+# It validates data quality before allowing the commit.
+#
+# Installation:
+#   ln -sf ../../.githooks/pre-commit-data-validation .git/hooks/pre-commit
+#
+# Or configure git hooks path:
+#   git config core.hooksPath .githooks
+
+# Check if any .dbn files are being added/modified
+DBN_FILES=$(git diff --cached --name-only --diff-filter=AM | grep '\.dbn$' || true)
+
+if [ -z "$DBN_FILES" ]; then
+    # No DBN files in this commit, skip validation
+    exit 0
+fi
+
+echo "════════════════════════════════════════════════════════"
+echo "Pre-commit: DBN Data Quality Validation"
+echo "════════════════════════════════════════════════════════"
+echo
+echo "Detected DBN file changes:"
+for file in $DBN_FILES; do
+    echo "  • $file"
+done
+echo
+
+# Extract symbols from filenames
+SYMBOLS=$(echo "$DBN_FILES" | xargs -n1 basename | cut -d'_' -f1 | sort -u)
+
+# Run validation for each affected symbol
+VALIDATION_FAILED=0
+
+for SYMBOL in $SYMBOLS; do
+    echo "Validating $SYMBOL..."
+
+    if ! cargo run --release --bin validate_dbn_data -- \
+        --symbol "$SYMBOL" \
+        --min-quality-score 60 \
+        --fail-on-poor-quality \
+        --format text >/dev/null 2>&1; then
+
+        echo "❌ Validation failed for $SYMBOL"
+        echo
+        echo "Run full validation to see details:"
+        echo "  cargo run --bin validate_dbn_data -- --symbol $SYMBOL"
+        echo
+        VALIDATION_FAILED=1
+    else
+        echo "✅ $SYMBOL passed validation"
+        echo
+    fi
+done
+
+if [ $VALIDATION_FAILED -eq 1 ]; then
+    echo "════════════════════════════════════════════════════════"
+    echo "❌ COMMIT BLOCKED: Data quality check failed"
+    echo "════════════════════════════════════════════════════════"
+    echo
+    echo "To skip this check (NOT RECOMMENDED):"
+    echo "  git commit --no-verify"
+    echo
+    exit 1
+fi
+
+echo "════════════════════════════════════════════════════════"
+echo "✅ All data quality checks passed"
+echo "════════════════════════════════════════════════════════"
+echo
+
+exit 0