Regenerate the manual page after the rebase onto the keyboard work

The rebase combined this branch's README additions with master's, and
index.html is generated from the README; manual-check passes on the
regenerated page.

docs/manual/index.html

@@ -172,6 +172,7 @@ purple included, and <code>None</code>. Each label is drawn with its initial on
 it reads without telling the colours apart, and the filter bar has a chip for
 each. In develop, the top bar names the open photograph's label and sets it,
 and the same keys work there.</p>
+<figure><img loading="lazy" src="media/library-labels.gif" alt="Labelling four frames with 6, 7, 8 and 9, taking one off with the same key, and filtering the grid to green"><figcaption>Labelling four frames with 6, 7, 8 and 9, taking one off with the same key, and filtering the grid to green</figcaption></figure>
 <h3 id="getting-about">Getting about</h3>
 <p>Drag the timeline to scrub through years; Ctrl and the wheel resize the
 thumbnails.</p>
@@ -217,8 +218,10 @@ Hold <code>Before</code> to see the photograph as it was.</p>
 <figure><img loading="lazy" src="media/develop-light.gif" alt="Raising exposure, pulling the highlights, lifting the shadows, then holding Before"><figcaption>Raising exposure, pulling the highlights, lifting the shadows, then holding Before</figcaption></figure>
 <h3 id="looking-closer">Looking closer</h3>
 <p>Double-click for 1:1; drag to move about; double-click again to fit. The
-wheel zooms to any amount in between.</p>
-<figure><img loading="lazy" src="media/develop-zoom.gif" alt="Zooming to 1:1, panning, and back"><figcaption>Zooming to 1:1, panning, and back</figcaption></figure>
+wheel zooms to any amount in between. Past 1:1 the file's own pixels are
+drawn as hard-edged blocks rather than smoothed, so what you see is what
+the sensor recorded.</p>
+<figure><img loading="lazy" src="media/develop-zoom.gif" alt="Zooming to 1:1, panning, then on in with the wheel until the pixels are blocks"><figcaption>Zooming to 1:1, panning, then on in with the wheel until the pixels are blocks</figcaption></figure>
 <h3 id="moving-between-photographs">Moving between photographs</h3>
 <p>The roll along the foot of the canvas holds the photographs the grid was
 showing; click one to open it. The right arrow, <code>D</code> or space opens the next,
@@ -235,6 +238,13 @@ refused, since a clipped pixel has no colour left to balance.</p>
 <p>Crop by dragging the frame's corners, straighten with the slider, lock a
 ratio from the chips. <code>Done composing</code> returns to the photograph.</p>
 <figure><img loading="lazy" src="media/compose.gif" alt="Cropping, straightening and choosing a ratio"><figcaption>Cropping, straightening and choosing a ratio</figcaption></figure>
+<p><code>Vertical</code> and <code>Horizontal</code>, under <code>Straighten</code>, correct the lines that
+converge when the camera is tilted up at a building; the crop refits to
+what is left.</p>
+<figure><img loading="lazy" src="media/compose-perspective.gif" alt="Standing towers shot from below upright with the Vertical slider"><figcaption>Standing towers shot from below upright with the Vertical slider</figcaption></figure>
+<p>A crop that leaves a mask wholly outside the frame says so, and offers to
+take the crop back or keep it.</p>
+<figure><img loading="lazy" src="media/crop-orphan.gif" alt="A stroke in a corner, a crop that leaves it outside, and the notice with Undo crop and Keep crop"><figcaption>A stroke in a corner, a crop that leaves it outside, and the notice with Undo crop and Keep crop</figcaption></figure>
 <h3 id="local-adjustments">Local adjustments</h3>
 <p><code>Local</code> in the rail turns the column into a mask stack. <code>Find subjects</code> runs a
 segmentation model over the photograph; what it recognises appears as a list
@@ -247,7 +257,10 @@ or shrink its edge, choose how it falls off. <code>Show masks as</code> draws th
 tinted, as alpha, or as an outline; the eye on its row switches it off.</p>
 <figure><img loading="lazy" src="media/local-paint.gif" alt="Looking at the mask three ways, painting into it, then growing its edge"><figcaption>Looking at the mask three ways, painting into it, then growing its edge</figcaption></figure>
 <p>Linear and radial gradients, a tone range and a colour range are the other
-ways to make one; each can be combined with any other.</p>
+ways to make one; each can be combined with any other. <code>∩ Intersect</code> keeps
+only where the new part and the mask agree: below, a gradient over the
+lower half, then two strokes that survive only where the gradient is.</p>
+<figure><img loading="lazy" src="media/local-intersect.gif" alt="A linear gradient, then Intersect and two painted strokes"><figcaption>A linear gradient, then Intersect and two painted strokes</figcaption></figure>
 <h3 id="repair">Repair</h3>
 <p><code>Repair</code> in the rail: click a mark and it is covered from a source DarkRoom
 chooses beside it. Drag either circle to move it; the size, feather and