Web dashboard v2 step 4: table-of-contents sidebar

Signed-in issue pages (issue, article, world, behind) get a chapter list
that marks where the reader is. One `issue_toc` helper builds it for all
four handlers: the picks in issue order numbered across sections, then
World Briefing, Behind the paper and a colophon anchor, with
position/total over the navigable chapters.

At `lg` and up it is a sticky left column with its own sticky header
(issue number, "Chapter N of M", a 2px progress bar); below `lg` the same
`<nav>` collapses behind a sticky hamburger bar and drops down as a
panel that closes on link tap, Escape and outside tap. Without JS the
panel is simply visible; `theme.js` marks the document scripted before
paint so it never flashes open. Article pages advance the progress bar
with scroll position through `requestAnimationFrame`, and the bar is a
`<progress>` element because a percentage width would need an inline
style the CSP forbids.

Also fixes the phone "ears" row from the step 2 review: the row no
longer wraps at 390px, the dateline has a short form below `sm:`, and
the toggle and account link stay on one line.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NHyYupFdBiR4VfoUM7NjSM

src/web/static/theme.js

@@ -1,4 +1,7 @@
 (() => {
+  // Marks the document as scripted before first paint so progressively enhanced
+  // widgets (the contents panel) can start collapsed without a flash.
+  document.documentElement.classList.add("has-js");
   try {
     const theme = localStorage.getItem("theme");
     if (theme === "light" || theme === "dark") document.documentElement.dataset.theme = theme;