chore: draw the toolbar icons in-tree with make icons (closes #378)

script/lib/icons.js draws the mark from geometry read back out of the
committed PNGs, since the coordinates were never recorded, and writes each
PNG with node's own zlib. `make icons` runs it and leaves alone a file that
already holds the drawn image.

tests/icons.test.js requires each committed file to hold exactly that
image: the same IHDR and every pixel. The compressed bytes are not
compared, because node's bundled zlib does not compress as the stock zlib
that made the committed files did; the decision is recorded on the issue.

build.js copies the manifests from MANIFEST_SOURCES instead of naming the
two paths a second time.

Model: opus-5-5

TODO.md

@@ -45,6 +45,16 @@ but the review is broader than any of them.
 
 # Completed Steps
 
+- 2026-10-07: The toolbar icons in `icons/` can be redrawn in the tree
+  ([#378](https://git.eeqj.de/sneak/AutistMask/issues/378)): `make icons` runs
+  `script/lib/icons.js`, which draws the mark and writes each PNG with node's
+  own `zlib`, no new dependency, leaving alone a file that already holds the
+  drawn image. `tests/icons.test.js` requires each committed file to hold
+  exactly that image, the same IHDR and every pixel. The compressed bytes are
+  not compared, because node's bundled zlib does not compress them as the stock
+  zlib that made the committed files did. `build.js` now copies each manifest
+  from the same path `copyIcons()` reads its icons from.
+
 - 2026-10-07: The README's end-to-end limits now match what the two browser
   suites do to the extension
   ([#293](https://git.eeqj.de/sneak/AutistMask/issues/293)). The `window.close`