chore: escape every value the views write as markup, and cut symbols on code points (closes #329)

The token screen's decimals and holder count, the ETH price, every address
total and each balance row's USD value went into innerHTML unescaped, against
the rule at the top of src/popup/views/helpers.js. They are escaped now. None
could carry markup, but formatUsd() writes a value under a cent as "< $0.01".

displaySymbol() counts a symbol in code points, not UTF-16 units, so the cut
never leaves half of an emoji, which rendered as U+FFFD.

explorerLink() was already removed on next.

Model: opus-5-5

TODO.md

@@ -45,6 +45,16 @@ but the review is broader than any of them.
 
 # Completed Steps
 
+- 2026-10-05: Escaping in the popup's views follows its own rule with no
+  exceptions ([#329](https://git.eeqj.de/sneak/AutistMask/issues/329)). The
+  decimals and holder count on a token's screen, and every USD figure (the ETH
+  price, each total and each balance row's value), went into `innerHTML`
+  unescaped; they are escaped now. None could carry markup, but `formatUsd()`
+  writes a value under a cent as `< $0.01`. `displaySymbol()` counts a symbol in
+  code points rather than UTF-16 units, so a cut never splits an emoji into a
+  half that renders as U+FFFD. `explorerLink()`, also named in the issue, was
+  already removed by [#168](https://git.eeqj.de/sneak/AutistMask/issues/168).
+
 - 2026-10-05: A Chrome end-to-end test that fails no longer takes later tests
   down with it ([#318](https://git.eeqj.de/sneak/AutistMask/issues/318)). Each
   test that turns a fixture switch on for itself alone (a held or failing gas