feat(console): filter match highlight + match count

- Highlight the matched substring (case-insensitive) in every visible line with a
  translucent yellow behind the text, drawn per wrap-segment like the selection highlight.
- Show a live match count next to the filter input ("N matches", red when zero).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/ui/windows/console_tab.h

@@ -152,6 +152,7 @@ private:
     
     // Output filter
     char filter_text_[128] = {0};
+    mutable int filter_match_count_ = 0;        // lines matching the text filter (for the toolbar)
     mutable std::vector<int> visible_indices_;  // Cached for selection mapping
     
     // Wrapped line height caching (for variable-height text wrapping)