Add backpressure stack for agentic coding quality gates

PostToolUse hooks run after every file edit:
- Backend: ./mvnw compile (Checkstyle Google Style + javac)
- Frontend: vue-tsc --noEmit + oxlint + ESLint

Stop hook runs test suites when source files changed, blocks the
agent on failure and re-engages it to fix the issue. Output is
filtered to [ERROR] lines only for context efficiency.

Static analysis: Checkstyle (validate phase), SpotBugs (verify phase),
ArchUnit (9 hexagonal architecture rules as JUnit tests).

Fail-fast: Surefire skipAfterFailureCount=1, Vitest bail=1.
Test log noise suppressed via logback-test.xml (WARN level),
redirectTestOutputToFile, and trimStackTrace.

Existing Java sources reformatted to Google Style (2-space indent,
import order, Javadoc on public types).

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

.claude/hooks/run-tests.sh

@@ -0,0 +1,54 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+cd "$CLAUDE_PROJECT_DIR"
+
+# Read hook input from stdin
+INPUT=$(cat)
+
+# Prevent infinite loops: if already re-engaged by a previous Stop hook, let it stop
+STOP_HOOK_ACTIVE=$(echo "$INPUT" | python3 -c "import sys,json; print(json.load(sys.stdin).get('stop_hook_active', False))" 2>/dev/null || echo "False")
+if [[ "$STOP_HOOK_ACTIVE" == "True" ]]; then
+    exit 0
+fi
+
+# Check for uncommitted changes in backend/frontend source
+HAS_BACKEND=$(git status --porcelain backend/src/ 2>/dev/null | head -1)
+HAS_FRONTEND=$(git status --porcelain frontend/src/ 2>/dev/null | head -1)
+
+# Nothing changed -- skip
+if [[ -z "$HAS_BACKEND" && -z "$HAS_FRONTEND" ]]; then
+    exit 0
+fi
+
+ERRORS=""
+PASSED=""
+
+# Run backend tests if Java sources changed
+if [[ -n "$HAS_BACKEND" ]]; then
+    if OUTPUT=$(cd backend && ./mvnw test -q 2>&1); then
+        PASSED+="✓ Backend tests passed. "
+    else
+        # Filter: only [ERROR] lines, skip Maven boilerplate
+        FILTERED=$(echo "$OUTPUT" | grep -E "^\[ERROR\]" | grep -v -E "Re-run Maven|See |Help 1|full stack trace|Failed to execute goal|For more information|^\[ERROR\] *$" || true)
+        ERRORS+="Backend tests failed:\n$FILTERED\n\n"
+    fi
+fi
+
+# Run frontend tests if TS/Vue sources changed
+if [[ -n "$HAS_FRONTEND" ]]; then
+    if OUTPUT=$(cd frontend && npm run test:unit -- --run 2>&1); then
+        PASSED+="✓ Frontend tests passed. "
+    else
+        ERRORS+="Frontend tests failed:\n$OUTPUT\n\n"
+    fi
+fi
+
+if [[ -n "$ERRORS" ]]; then
+    # Block stopping — re-engage the agent to fix failures
+    ESCAPED=$(printf '%s' "$ERRORS" | python3 -c "import sys,json; print(json.dumps(sys.stdin.read()))")
+    echo "{\"decision\":\"block\",\"reason\":$ESCAPED}"
+else
+    # Success — allow stopping, report via stopReason
+    echo "{\"decision\":\"approve\",\"reason\":\"$PASSED\"}"
+fi