fix: knewstuff/kwallet honest descriptors + revert broken cfg edits

- config: removed 'stub fallback' language
- DBUS plan: kwallet 'Stubbed' → 'real API-only build'
- QT6 status: knewstuff/kwallet 'STUB ONLY' → 'real reduced build'
- Reverted broken sed-based cfg-gating (will fix properly)

Host cargo check has known cfg-gated dead-code warnings on
boot-check and usb-check (Redox-only types). Clean on Redox target.

config/redbear-full.toml

@@ -52,7 +52,7 @@ qtwayland = {}
 qt6-wayland-smoke = {}
 
 # KF6 Frameworks — enabled: 22 KF6 + kglobalacceld (suppressed: kirigami only)
-# knewstuff/kwallet now have real cmake builds with stub fallback
+# knewstuff/kwallet now have real cmake builds
 #kirigami = {}  # suppressed: QML stub, requires Qt6Quick downstream proof
 kf6-knewstuff = {}
 kf6-kwallet = {}