Bound the prompt panel's bar by wrapped rows #453

Parent

Spec: bound the prompt panel's bar by wrapped rows, not characters

What to build

ctui draws the person's own prompts as a panel with a thin ┃ bar down its left edge, built as one ┃ per character of the prompt plus three. A 20,000-character paste therefore builds a 20,000-row text element for a panel a few dozen rows tall, rebuilt on every transcript draw.

After this ticket the panel looks exactly as it does today — the bar still reaches the bottom of every prompt, long or short, and the row still clips — but the bar is only as long as the prompt can possibly be once wrapped.

The bound is the wrapped row count per line against a quarter of the inner width, which is the pessimistic cells-per-row figure once wide characters and long unbreakable words are in play, clamped so it can never exceed today's character count:

cells   = max(1, floor(inner / 4))
rows    = sum over the prompt's lines of max(1, ceil(line length / cells)) + 3
length  = min(rows, character count + 3)      // never longer than today

The inner width is derived, not measured: the transcript's column count less the panel's five cells of chrome less the gap a docked Sidebar takes, floored at one. The rewrite takes the viewport's column count as a new optional input, passed from the render event for the person's own prompts; given none, the bar keeps today's character-count length.

Note the naive ceil(length / inner) is a lower bound and would stop the bar partway down the panel. Ships on bugfix/plugin-authoring-review.

Acceptance criteria

• A long single-line prompt with a viewport draws a bar far shorter than its character count, and long enough to reach the bottom of the panel at that width.
• A prompt of many short lines counts each line's own wrap.
• The bar is never longer than today's character count plus three, at any width.
• With no viewport, the bar is today's character-count length, unchanged.
• The docked gap is accounted for in the inner width, and no new dock argument is introduced: the gap the rewrite already receives is the Sidebar's.
• The panel's look is untouched: margin, padding, overflow, background, the bar's colour, the removal of paste tags and edge newlines, and which prompt origins ctui rewrites at all.
• Held by unit tests at the existing mount seam for transcript rewrites, one mount with a viewport and one without.
• node scripts/check.ts exits 0.