Convert SVG textPath to transform matrix

Question

I have in an e-book a title page formatted with SVG, using textPath to place text along a curve:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" version="1.1" viewBox="0 0 160 256" width="160" height="256">
  <g style="text-align:center;text-anchor:middle;stroke:none;stroke-width:0;">
    <path style="fill:none;"
      d="m 0,72 c 32,-16 52,-20 80,-20 28,0 48,4 80,20"
      id="path-upper" />
    <text style="font-size:9px;"><textPath xlink:href="#path-upper" startOffset="50%"><tspan>Text to be Placed Along a Curve</tspan></textPath></text>
  </g>
</svg>

The trouble is that many e-book platforms (most importantly the Kindle) do not support textPath. What I’d like to do is “compile out” the results of textPath into rotated text.

Running

$ inkscape -A curve.pdf --export-ignore-filters curve.svg
$ inkscape -l curve2.svg curve.pdf

does kinda work, yielding (for example)

<text transform="matrix(0.94068351,0.33928532,0.33928532,-0.94068351,17.864857,145.9156)"><tspan y="0" x="0">T</tspan></text>
<text transform="matrix(0.94997891,0.31231406,0.31231406,-0.94997891,20.665461,146.93493)"><tspan y="0" x="0">e</tspan></text>
<text transform="matrix(0.96048875,0.27831882,0.27831882,-0.96048875,24.497618,148.19598)"><tspan y="0" x="0">x</tspan></text>
<text transform="matrix(0.96875188,0.24803186,0.24803186,-0.96875188,28.337099,149.29823)"><tspan y="0" x="0">t</tspan></text>

but it also rewrites the rest of my SVG file—most annoyingly, adding a global transform (transform="matrix(1.3333333,0,0,-1.3333333,0,256)") which makes everything harder to read and understand.

Is there another tool or bit of code I can use to programmatically generate these rotation matrices from the path?

_{(Otherwise, what I need is a tool that combines the transform matrices within the SVG file after Inkscape has mangled things, but that’s a different question.)}