Support multi-click transcript selection using transcript/viewport
coordinates
(wrapped visual line index + content column), not terminal buffer
positions.
Gestures:
- double click: select word-ish token under cursor
- triple click: select entire wrapped line
- quad click: select paragraph (contiguous non-empty wrapped lines)
- quint+ click: select the entire history cell (all wrapped lines
belonging to a
single `HistoryCell`, including blank lines inside the cell)
Selection expansion rebuilds the wrapped transcript view from
`HistoryCell::display_lines(width)` so boundaries match on-screen
wrapping during
scroll/resize/streaming reflow. Click grouping is resilient to minor
drag jitter
(some terminals emit tiny Drag events during clicks) and becomes more
tolerant as
the sequence progresses so quad/quint clicks are practical.
Tests cover expansion (word/line/paragraph/cell), sequence resets
(timing, motion,
line changes, real drags), drag jitter, and behavior on spacer lines
between
history cells (paragraph/cell selection prefers the cell above).
Avoid distracting 1-cell highlights on simple click by tracking an
anchor on mouse down and only creating a visible selection once the
mouse is dragged (selection head set).
When dragging while following the bottom during streaming, request a
scroll lock so the viewport stops moving under the active selection.
Move selection state transitions into transcript_selection helpers
(returning change/lock outcomes for the caller) and add unit tests for
the state machine.
Copy now operates on the full logical selection range (anchor..head),
not just the visible viewport, so selections that include offscreen
lines copy the expected text.
Selection extraction is factored into `transcript_selection` to make the
logic easier to test and reason about. It reconstructs the wrapped
visual transcript, renders each wrapped line into a 1-row offscreen
Buffer, and reads the selected cells. This keeps clipboard text aligned
with what is rendered (gutter, indentation, wrapping).
Additional behavior:
- Skip continuation cells for wide glyphs (e.g. CJK) so copied text does
not include spurious spaces like "コ X".
- Avoid copying right-margin padding spaces.
Manual tested performed:
- "tell me a story" a few times
- scroll up, select text, scroll down, copy text
- confirm copied text is what you expect
