Extend issue context popup beyond markdown content (#36908)

Extend the issue context popup beyond markdown. Any link rendered with
the `ref-issue` class now gets the popup, which covers commit titles and
issue titles everywhere they appear (repo home, commits list, blame,
branches, graph, PR commits, issue/PR pages, compare, …). For surfaces
that synthesize links without markdown autolinking (dashboard activity
feed, pulse page, commit merged-PR line), opt in by adding
`data-ref-issue-container` on a parent (or `ref-issue` on the link).

- Use `html_url` from the backend payload instead of synthesizing links
client-side
- Fetch outside the component, stateless, with a per-URL cache
- Small hover delay so passing over a link doesn't fire a request
- Drop the loading state (shifted layout)
- Make both links in the tooltip work; prevent nested tooltips
- Fix feed title `<a>` width so the tooltip only shows on link hover

Co-authored-by: Claude (Opus 4.6) <noreply@anthropic.com>

web_src/js/index.ts

@@ -63,6 +63,7 @@ import {initGlobalComboMarkdownEditor, initGlobalEnterQuickSubmit, initGlobalFor
 import {callInitFunctions} from './modules/init.ts';
 import {initRepoViewFileTree} from './features/repo-view-file-tree.ts';
 import {initActionsPermissionsForm} from './features/common-actions-permissions.ts';
+import {initRefIssueContextPopup} from './features/ref-issue.ts';
 import {initGlobalShortcut} from './modules/shortcut.ts';
 import {initDevtest} from './modules/devtest.ts';
 
@@ -98,6 +99,7 @@ const initPerformanceTracer = callInitFunctions([
   initImageDiff,
   initMarkupAnchors,
   initMarkupContent,
+  initRefIssueContextPopup,
   initSshKeyFormParser,
   initStopwatch,
   initTableSort,