feat(ui): registration wizard — fit the cut to the sticker from three jogged points

[BernardJen]

Why

1.1.0's registration (touch-mark each point, read the miss, shift work zero) could only correct a translation, and only by moving the origin. A sticker mounted a few degrees off — the normal case by hand — could not be cut. The operator asked for a wizard that measures where the sticker really is and moves the cut to it. OpenSpec change svg-calibration-points, revised.

What

• Registration wizard (src/ui/RegistrationWizard.tsx), opened automatically after importing an SVG with ≥2 calibration points and via Register…: mount → per point jog onto the crosshair (arrow keys / arrows, step, pen up/down) and Set → result → Apply.
• fitRegistration (src/plot/register.ts): 2-D rigid least squares (rotation + translation, scale fixed at 1:1) in the placePolylines convention, so the result is a Placement. Reports per-point residuals, RMS and the implied print scale; the wizard flags RMS > 0.3 mm or scale off > 1%.
• Removed the 1.1.0 Run calibration / Apply correction UI, shiftWorkZero (controller, protocol, gateway, client) and generateCalibrationGcode. The streamProgram busy guard stays.
• Shared button styles moved to src/ui/styles.ts. README section rewritten, changelog, v1.2.0.

Design notes

• Scale is not solved for on purpose: the sticker is printed 1:1; stretching the cut to a mis-jogged point would be wrong. The implied scale is a warning.
• The warning is on RMS, not on one residual: least squares shares a single point's error across all points, so the mis-set point is not reliably the largest residual. A unit test pins this down.

Verification

• mise run ci green, 97 tests, coverage 55% statements.
• fitRegistration round-trips known placements (translation, ±rotation incl. ≈180°), flags a 1.5 mm mis-set point via RMS, reports a 2% print scale without applying it, handles 2/1/0 points.
• Chromium with a seeded session: Registration panel lists cal-P1..3 at page 15,15 / 195,15 / 15,282; Register… opens the wizard; mount and point steps render, Set disabled with the reason while disconnected.
• Hardware (tasks 7.1–7.4): mount a sticker a few degrees off, run the wizard, confirm the fitted angle/offset and RMS < 0.3 mm, cut, confirm the contour follows the print.

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