chore(pilot): remove deprecated SuggestedFix task-lane card

Superseded by ProposalBanner (Phase 8). The import was already removed
from AssistantChatPage in the previous commit; this deletes the orphaned
file itself and strips the now-unused suggestedFixSlot prop from
TaskLane's interface and both call sites.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/pages/AssistantChatPage.tsx

@@ -1614,7 +1614,6 @@ export default function AssistantChatPage() {
                     loading={loading}
                   />
                 }
-                suggestedFixSlot={null}
                 bottomSlot={
                   <>
                     {scriptPanelOpen && activeFix && activeChatId && (
@@ -1694,7 +1693,6 @@ export default function AssistantChatPage() {
               loading={loading}
             />
           }
-          suggestedFixSlot={null}
           bottomSlot={
             <>
               {scriptPanelOpen && activeFix && activeChatId && (