fix(ui): F8-09 owner-feedback — fixed TOC trigger + heading offset (#52)

Owner-reported regressions in Firefox + Safari on desktop after the
initial F8-09 patch landed:

1. The TOC trigger rode up with the page during scroll instead of
   staying pinned to the viewport (mobile worked, desktop did not).
2. Clicking a popover item scrolled the matching section so its
   heading went up under the chrome — only the table body was visible.

Root cause for (1): the in-game shell declares `overflow-y: auto`
on `.active-view-host` so mobile (where `.game-shell` is fixed at
`inset: 0`) has an internal scroll region. On desktop the host
grows with content, no overflow ever engages, and the document
body becomes the actual scroll container. Per CSS spec the host
remains the "scrollport" for any `position: sticky` descendant, so
the trigger inside the report column never sees the scroll event
and rides up with the body content.

Fix:

- Swap the trigger from `position: sticky` to `position: fixed`.
  The component is mounted only while the report active view is on
  screen, so the fixed element is naturally tied to the view's
  lifetime. Anchor at `top: 4rem` (below the in-game header), and
  on `min-width: 1024px` shift `right` by 18 rem to clear the
  always-on sidebar; below 1024 px the sidebar is an overlay so
  the default `right: 1.25rem` matches the report's right padding.
- Add `padding-top: 4.5rem` to `.report-view` (4rem mobile) so the
  first section heading does not land under the trigger at scroll
  position 0.
- Add `scroll-margin-top: 7.5rem` to every `<section
  id="report-…">` so `scrollIntoView({ block: "start" })` lands
  the heading below the trigger after a popover-driven jump.
- Sync `ui/docs/report-view.md` §"Table of contents and active
  highlight" with the new positioning rationale.

Tests: `pnpm check`, `pnpm test` (821), `pnpm test:e2e
report-sections` (4 projects) all green.

Refs: #52 (#43 umbrella).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

ui/docs/report-view.md

@@ -85,8 +85,8 @@ the body — both surfaces stay in sync by construction.
 
 ## Table of contents and active highlight
 
-`report/report-toc.svelte` renders a single sticky icon-popup
-trigger in the top-right corner of the report column. The trigger
+`report/report-toc.svelte` renders a single icon-popup trigger
+pinned to the top-right corner of the report column. The trigger
 shows `≡` followed by the title of the currently-active section
 (CSS-clamped with `text-overflow: ellipsis` so a long RU title
 cannot bloat the button). Clicking opens an anchored popover
@@ -97,8 +97,29 @@ the matching `<section id="report-<slug>">` into view via
 `scrollIntoView` (with `prefers-reduced-motion` falling back to
 `behavior: "auto"`).
 
-On viewports below `768.98 px` the same surface re-styles into a
-fixed bottom-sheet anchored above the layout-owned bottom-tabs
+The trigger uses `position: fixed` instead of `position: sticky`.
+Per the CSS sticky spec a sticky element sticks within its nearest
+ancestor with non-`visible` overflow — and `.active-view-host`
+declares `overflow-y: auto` for the mobile scroll story. On
+desktop the host grows with content and the document body becomes
+the actual scroll container, so a sticky trigger inside the report
+column never receives a scroll event and rides up with the page
+content. A fixed trigger sidesteps the chain entirely; the
+component is mounted only while the report active view is on
+screen, so the fixed element is naturally tied to the view's
+lifetime. The desktop offset is `right: calc(18 rem + 1.25 rem)`
+to clear the always-on `lib/sidebar/sidebar.svelte`; below
+1024 px the sidebar collapses to an overlay drawer, so the
+default `right: 1.25 rem` matches the report's right padding. The
+report-view itself adds a top padding equal to the trigger's
+viewport offset plus its height so the first section's heading
+does not render under the trigger at scroll position 0, and every
+`<section id="report-…">` gets `scroll-margin-top: 7.5rem` so
+`scrollIntoView({ block: "start" })` lands the heading below the
+trigger after a popover-driven jump.
+
+On viewports below `768.98 px` the popover surface re-styles into
+a fixed bottom-sheet anchored above the layout-owned bottom-tabs
 bar (mirrors `lib/active-view/map-toggles.svelte`), so the same
 trigger and the same menuitem list serve desktop and mobile.