Part of #885: the Transform effect's dialog takes Transform Each's controls

[bflatastic]

Part of #885.

Effect › Distort & Transform › Transform… was a plain list of fields. It now has Object › Transform › Transform Each's layout, kept with the effect so editing it from the Appearance panel shows the same values:

• Scale and Move with sliders beside their fields (the fields take values past the rails), Rotate with an angle dial (drag to point it, Shift for 45° steps).
• Options: Copies, Reflect X, Reflect Y, the 9-point reference point and Random.
• The effect itself: it scales, rotates and reflects about the chosen reference point (reference, 0–8, the centre by default). Random applies a share of each value, drawn from the object's id: each object varies its own way and keeps its result on every redraw, and a group's members move together. Copies stop before one reaches past 1e9 pt and scale and move are capped, so huge values can't overflow.
• Transform Each and the effect share one implementation of the sections and options; the angle dial is a new widget.
• A plain number field now takes the keyboard focus when it's a dialog's first field, so both dialogs open with Scale › Horizontal selected for typing (Transform Each used to open on Move › Horizontal).
• MCP/control: effect.dialog {effect: "distort.transform"} takes reference and random; the effect catalogue documents them. docs/control-protocol.md and ROADMAP updated.

Still missing, and listed in the ROADMAP: the Transform Objects, Transform Patterns and Scale Strokes & Effects options, because geometry effects only reshape paths so far.

Tested:

• cargo xtask ci (all 7 steps); all 863 ui-egui tests.
• New tests: the reference point (scale, rotate, reflect about corners and edges), Random's stability and range, copies stopping before overflow, a random Transform on a group moving its members together, the dialog's controls, preview and reopening from the Appearance panel, and typing straight into Scale › Horizontal in Transform Each and the effect.
• Live: Transform with 3 copies, 40 pt move, 15° rotation about the bottom-left point previews as expected on the canvas, with the new controls laid out as above.

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