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/fetch.py

@@ -3,19 +3,20 @@ RSS feed fetching, Project Gutenberg parsing, and headline caching.
 Depends on: config, sources, filter, terminal.
 """
 
-import re
 import json
 import pathlib
+import re
 import urllib.request
 from datetime import datetime
 
 import feedparser
 
 from engine import config
+from engine.filter import skip, strip_tags
 from engine.sources import FEEDS, POETRY_SOURCES
-from engine.filter import strip_tags, skip
 from engine.terminal import boot_ln
 
+
 # ─── SINGLE FEED ──────────────────────────────────────────
 def fetch_feed(url):
     try: