refactor: deduplicate code, remove unused code, improve CI/CD

Code deduplication:
- Create CSVValueParser for shared parsing logic (decoder)
- Create CSVValueFormatter for shared encoding logic (encoder)
- Create StreamingRowProcessor for streaming decode pattern
- Extract adjustedBuffer helper to CSVUtilities
- Use encodeValue/processAsyncRow to eliminate duplication

Dead code removal:
- Remove unused FieldBufferPool class and tests
- Mark unused protocol parameters with underscore prefix

CI/CD improvements:
- Merge release.yml into ci.yml with 4-stage pipeline
- Add code quality checks (format, duplicates, unused)
- Add CodeQL security analysis
- Add test coverage reporting
- Add SPM dependency caching
- Use .spk.json for version management
- Add benchmark results to release notes

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: g-cqd

.githooks/pre-commit

@@ -0,0 +1,23 @@
+#!/bin/sh
+# SwiftProjectKit pre-commit hook
+
+# Use global spk if available, otherwise download latest release
+if command -v spk >/dev/null 2>&1; then
+    exec spk hooks run pre-commit
+else
+    SPK=".build/spk"
+    if [ ! -x "$SPK" ]; then
+        echo "Downloading latest spk..."
+        mkdir -p .build
+        ARCH=$(uname -m)
+        case "$ARCH" in
+            arm64) SUFFIX="macos-arm64" ;;
+            x86_64) SUFFIX="macos-x86_64" ;;
+            *) SUFFIX="macos-universal" ;;
+        esac
+        LATEST_URL=$(curl -sI "https://github.com/g-cqd/SwiftProjectKit/releases/latest" | grep -i "^location:" | sed 's/.*tag\///' | tr -d '\r\n')
+        curl -sL "https://github.com/g-cqd/SwiftProjectKit/releases/download/${LATEST_URL}/spk-${LATEST_URL#v}-${SUFFIX}.tar.gz" | tar -xzf - -C .build
+        chmod +x "$SPK"
+    fi
+    exec "$SPK" hooks run pre-commit
+fi

.githooks/pre-push

@@ -0,0 +1,23 @@
+#!/bin/sh
+# SwiftProjectKit pre-push hook
+
+# Use global spk if available, otherwise download latest release
+if command -v spk >/dev/null 2>&1; then
+    exec spk hooks run pre-push
+else
+    SPK=".build/spk"
+    if [ ! -x "$SPK" ]; then
+        echo "Downloading latest spk..."
+        mkdir -p .build
+        ARCH=$(uname -m)
+        case "$ARCH" in
+            arm64) SUFFIX="macos-arm64" ;;
+            x86_64) SUFFIX="macos-x86_64" ;;
+            *) SUFFIX="macos-universal" ;;
+        esac
+        LATEST_URL=$(curl -sI "https://github.com/g-cqd/SwiftProjectKit/releases/latest" | grep -i "^location:" | sed 's/.*tag\///' | tr -d '\r\n')
+        curl -sL "https://github.com/g-cqd/SwiftProjectKit/releases/download/${LATEST_URL}/spk-${LATEST_URL#v}-${SUFFIX}.tar.gz" | tar -xzf - -C .build
+        chmod +x "$SPK"
+    fi
+    exec "$SPK" hooks run pre-push
+fi