feat: Exit on first Python callback exception (closes #133)

By default, McRogueFace now exits with code 1 on the first unhandled
exception in timer, click, key, or animation callbacks. This prevents
repeated exception output that wastes resources in AI-driven development.

Changes:
- Add exit_on_exception config flag (default: true)
- Add --continue-after-exceptions CLI flag to preserve old behavior
- Update exception handlers in Timer, PyCallable, and Animation
- Signal game loop via McRFPy_API atomic flags
- Return proper exit code from main()

Before: Timer exceptions repeated 1000+ times until timeout
After: Single traceback, clean exit with code 1

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

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

tests/notes/test_exception_exit_manual.sh

@@ -0,0 +1,38 @@
+#!/bin/bash
+# Manual test for --continue-after-exceptions feature (Issue #133)
+#
+# This test must be run manually because it verifies exit codes
+# rather than test output.
+
+echo "Testing --continue-after-exceptions feature..."
+echo
+
+cd "$(dirname "$0")/../../build"
+
+# Test 1: Default behavior - should exit with code 1 on first exception
+echo "Test 1: Default behavior (exit on first exception)"
+timeout 5 ./mcrogueface --headless --exec ../tests/notes/test_exception_exit.py 2>&1
+EXIT_CODE=$?
+echo "Exit code: $EXIT_CODE"
+if [ $EXIT_CODE -eq 1 ]; then
+    echo "[PASS] Exit code is 1 as expected"
+else
+    echo "[FAIL] Expected exit code 1, got $EXIT_CODE"
+    exit 1
+fi
+echo
+
+# Test 2: --continue-after-exceptions - should keep running until timeout
+echo "Test 2: --continue-after-exceptions (continue after exception)"
+timeout 1 ./mcrogueface --headless --continue-after-exceptions --exec ../tests/notes/test_exception_exit.py 2>&1 | tail -5
+EXIT_CODE=${PIPESTATUS[0]}
+echo "Exit code: $EXIT_CODE"
+if [ $EXIT_CODE -eq 124 ]; then
+    echo "[PASS] Timeout killed it (exit code 124) - continued running as expected"
+else
+    echo "[FAIL] Expected exit code 124 (timeout), got $EXIT_CODE"
+    exit 1
+fi
+echo
+
+echo "All tests PASSED!"