Transcript actions menu covers the knot's own response text when opened

[hlship]

The per-knot actions menu (`knot-menu.ts`'s `renderKnotMenu`) is shared verbatim between the graph pane and the transcript - the only difference is direction (`PANE_CONFIG` in `knot-menu.ts`): the graph pane opens rightward (`dropdown-right`), the transcript opens leftward (`dropdown-left`), since its trigger sits at the far-right edge of a full-width row and opening rightward would clip off the window.

In the graph pane that lands the menu over mostly-blank canvas. In the transcript, opening leftward lands it directly on top of that row's own response text, obscuring it while the menu is open.

This isn't a layout bug - the popup is `position: fixed` at all times (`.knot-menu-popover` in `styles/input.css`), so it never reflows the transcript text, it just visually overlaps it (normal dropdown-menu behavior, but more disruptive here since the covered content is exactly what the user is reading).

Possible fixes, not yet decided:

• Anchor the transcript menu above/below its trigger instead of leftward-over-the-row, so it only covers a line or two instead of the row's full width.
• Add a stronger shadow/border for visual separation without changing position.
• Leave as-is (standard dropdown-covers-content behavior).

Screenshot showing the overlap: menu opened on the "look" knot obscures its diff text mid-line.