Four view modules (search, command_palette, file_history, trace) each had
their own copy of cursor_cell_offset / text_cell_width for converting a
byte-offset cursor position to a display-column offset. Phase 5 introduced
a proper text_width module with these functions; this commit removes the
duplicates and rewires all call sites to use crate::text_width.
- search.rs: removed local text_cell_width + cursor_cell_offset definitions
- command_palette.rs: removed local cursor_cell_offset definition
- file_history.rs: replaced inline chars().count() cursor calc with import
- trace.rs: replaced inline chars().count() cursor calc with import
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