style: apply ruff auto-fixes across codebase

- Fix import sorting (isort) across all engine modules
- Fix SIM105 try-except-pass patterns (contextlib.suppress)
- Fix nested with statements in tests
- Fix unused loop variables

Run 'uv run pytest' to verify tests still pass.

engine/app.py

@@ -2,23 +2,33 @@
 Application orchestrator — boot sequence, signal handling, main loop wiring.
 """
 
-import sys
-import os
-import time
-import signal
 import atexit
+import os
+import signal
+import sys
 import termios
+import time
 import tty
 
 from engine import config, render
-from engine.terminal import (
-    RST, G_HI, G_MID, G_DIM, W_DIM, W_GHOST, CLR, CURSOR_OFF, CURSOR_ON, tw,
-    slow_print, boot_ln,
-)
 from engine.fetch import fetch_all, fetch_poetry, load_cache, save_cache
-from engine.ntfy import NtfyPoller
 from engine.mic import MicMonitor
+from engine.ntfy import NtfyPoller
 from engine.scroll import stream
+from engine.terminal import (
+    CLR,
+    CURSOR_OFF,
+    CURSOR_ON,
+    G_DIM,
+    G_HI,
+    G_MID,
+    RST,
+    W_DIM,
+    W_GHOST,
+    boot_ln,
+    slow_print,
+    tw,
+)
 
 TITLE = [
     "  ███╗   ███╗ █████╗ ██╗███╗   ██╗██╗     ██╗███╗   ██╗███████╗",