## Summary
Seed the text_finder's query from the focused pane's item instead of
only the active center editor. Selecting text in the terminal or
markdown_preview and opening text_finder now seeds that selection; the
item next to focus wins when both it and a center editor have
selections. If the focused item has no selection, the center item is
tried, then the last persisted search as before.

## Test plan
- Select a word in the terminal, open Text Finder, confirm it's
pre-filled and searching
- With a selection in both terminal and editor, confirm the focused one
wins
- Focus the terminal without a selection, confirm an editor selection
still seeds
- No selection anywhere, confirm the last search is restored
- Confirm a selection in a markdown preview seeds too

Release Notes:

- Improved the Text Finder to seed its query from the focused item's
selection, including the terminal

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Co-authored-by: ozacod <ozacod@users.noreply.github.com>