Address review findings in the app, server and tests

- app: startup shell, python and ssh probes run asynchronously so a slow
  shell profile can't freeze the window; PATH comes from the user's real
  login shell and a failed lookup isn't cached; a server that never
  answers is killed; the setup offer runs once per launch, only after the
  UI loads, and decides from HostName alone; connect.sh is started through
  `env ... zsh` so it works whatever the login shell is.
- server: volume validates the level before muting or changing anything.
- Steam: null-safe install-manager fields, http.client errors caught in
  store ratings, price fallback when a sale has no final price.
- tests: server output kept for diagnosis, any startup error retried, and
  captures asserted non-cacheable.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

ui/frame_store.py

@@ -6,6 +6,7 @@ Uses the store's public endpoints (no key, no login):
                                                `frame_resolved_category` is the Frame's
 Buying happens on the store page, signed in as the user; nothing here buys.
 """
+import http.client
 import json
 import threading
 import time
@@ -37,7 +38,7 @@ def frame_rating(appid):
         r = _get("saleaction/ajaxgetdeckappcompatibilityreport", {"nAppID": appid, "l": "english"})
         cat = int((r.get("results") or {}).get("frame_resolved_category") or 0)
         cat = cat if 0 <= cat <= 3 else 0
-    except (OSError, ValueError, TypeError, AttributeError):
+    except (OSError, ValueError, TypeError, AttributeError, http.client.HTTPException):
         return 0  # not cached, so the next search retries
     with _lock:
         _compat[appid] = (time.time(), cat)