feat(daemon): add display abstraction and daemon mode with C&C

engine/display.py

@@ -0,0 +1,102 @@
+"""
+Display output abstraction - allows swapping output backends.
+
+Protocol:
+    - init(width, height): Initialize display with terminal dimensions
+    - show(buffer): Render buffer (list of strings) to display
+    - clear(): Clear the display
+    - cleanup(): Shutdown display
+"""
+
+import time
+from typing import Protocol
+
+
+class Display(Protocol):
+    """Protocol for display backends."""
+
+    def init(self, width: int, height: int) -> None:
+        """Initialize display with dimensions."""
+        ...
+
+    def show(self, buffer: list[str]) -> None:
+        """Show buffer on display."""
+        ...
+
+    def clear(self) -> None:
+        """Clear display."""
+        ...
+
+    def cleanup(self) -> None:
+        """Shutdown display."""
+        ...
+
+
+def get_monitor():
+    """Get the performance monitor."""
+    try:
+        from engine.effects.performance import get_monitor as _get_monitor
+
+        return _get_monitor()
+    except Exception:
+        return None
+
+
+class TerminalDisplay:
+    """ANSI terminal display backend."""
+
+    def __init__(self):
+        self.width = 80
+        self.height = 24
+
+    def init(self, width: int, height: int) -> None:
+        from engine.terminal import CURSOR_OFF
+
+        self.width = width
+        self.height = height
+        print(CURSOR_OFF, end="", flush=True)
+
+    def show(self, buffer: list[str]) -> None:
+        import sys
+
+        t0 = time.perf_counter()
+        sys.stdout.buffer.write("".join(buffer).encode())
+        sys.stdout.flush()
+        elapsed_ms = (time.perf_counter() - t0) * 1000
+
+        monitor = get_monitor()
+        if monitor:
+            chars_in = sum(len(line) for line in buffer)
+            monitor.record_effect("terminal_display", elapsed_ms, chars_in, chars_in)
+
+    def clear(self) -> None:
+        from engine.terminal import CLR
+
+        print(CLR, end="", flush=True)
+
+    def cleanup(self) -> None:
+        from engine.terminal import CURSOR_ON
+
+        print(CURSOR_ON, end="", flush=True)
+
+
+class NullDisplay:
+    """Headless/null display - discards all output."""
+
+    def init(self, width: int, height: int) -> None:
+        self.width = width
+        self.height = height
+
+    def show(self, buffer: list[str]) -> None:
+        monitor = get_monitor()
+        if monitor:
+            t0 = time.perf_counter()
+            chars_in = sum(len(line) for line in buffer)
+            elapsed_ms = (time.perf_counter() - t0) * 1000
+            monitor.record_effect("null_display", elapsed_ms, chars_in, chars_in)
+
+    def clear(self) -> None:
+        pass
+
+    def cleanup(self) -> None:
+        pass