Make mouth width and zoom distortion resolution-invariant

[rhotacizer]

Fixes two issues causing the pose of the puppet to vary depending on the size or resolution of the canvas:

• The width of the mouth is multiplied by an extra scale factor, resulting in a mouth width proportional to the square of the canvas size.
• The zoom distortion uses a constant conversion from z depth (in pixels) to x and y scaling factors (in body space), when this should be resolution-dependent.

(I noticed these changes trying to render the puppet in higher resolution on a Mac retina display.)

Pose channels

{
    "hrx": 0, "hry": 0,
    "bx": 0, "by": 0,
    "eby": 0, "ebx": 0,
    "e0y": 1, "e1y": 1,
    "ex": 0, "ey": 0, "ez": 1,
    "ny": 0,
    "mx": -0.75, "my": 1,
    "mly": 0.5, "mlz": 0,
    "mty": 0.2, "mtz": 0.5,
    "mcx": 0,
    "teeth": 0,
    "rhx": 0, "rhy": 0, "rhz": 0, "rh": 0,
    "rbx": 0.2, "rby": -1.6, "rbz": 0.5, "rb": 1,
    "rax": 0, "ray": 0, "raz": 0, "ra": 0,
    "rpx": 0, "rpy": 0, "rpz": 0,
    "rrz": -90, "rrx": 108, "rry": -18,
    "ri0": 0, "ri1": 0, "ri2": 0, "ris": 0,
    "rm0": 1, "rm1": 1, "rm2": 0.5, "rms": 0,
    "rr0": 1, "rr1": 1, "rr2": 0.5, "rrs": 0,
    "rp0": 1, "rp1": 1, "rp2": 0.5, "rps": 0,
    "rt0x": 0, "rt0y": 0.5, "rt1x": 0.25, "rt1y": 0.5, "rt2x": 0.25,
    "lhx": 0, "lhy": 0, "lhz": 0, "lh": 0,
    "lbx": 0, "lby": 1, "lbz": 0, "lb": 1,
    "lax": 0, "lay": 0, "laz": 0, "la": 0,
    "lpx": 0, "lpy": 0, "lpz": 0,
    "lrz": 0, "lrx": -90, "lry": 0,
    "li0": 0, "li1": 0, "li2": 0, "lis": 0,
    "lm0": 0, "lm1": 0, "lm2": 0, "lms": 0,
    "lr0": 0, "lr1": 0, "lr2": 0, "lrs": 0,
    "lp0": 0, "lp1": 0, "lp2": 0, "lps": 0,
    "lt0x": 0, "lt0y": 0, "lt1x": 0, "lt1y": 0, "lt2x": 0
}

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