Plan: Search window redesign

A full redesign of the search dialog: unified bar + mode chips, filter chips with popovers, AI transparency strip, empty state with examples, recent searches (persisted), auto-apply with IME-safe debounce, dialog state preservation, search-results virtual volume for "Open in pane", per-row context menus, clickable path pills, and an MCP open_search_dialog tool. Plan iterated through four rounds of reviewer feedback before commit.

Author: vdavid