Changelog

Root cause: deduplication used URL-only comparison, but feeds where

all entries share the same link (e.g., changelog feeds pointing to

/changelog) would reject every article after the first as a "duplicate".

Fix: add EntryId field to RssArticle populated from the Atom <id> or

RSS <guid> element. Dedup now checks entry ID first (globally unique

per spec), falling back to URL comparison for feeds without entry IDs.

Adds BacklinkService.PreBuildIndexAsync() and calls it during the

deferred background services block in App.axaml.cs. This eliminates

the ~700ms cold-start delay when the user first clicks an item with

the Info Panel open, since the cross-plugin backlink index is already

warm by the time they interact.

The existing SemaphoreSlim guard in EnsureIndexBuiltAsync ensures

concurrent calls (from a user click racing the startup pre-build)

are safe. If the pre-build fails, the index falls back to lazy

initialization on first query (existing behavior).

MenuFlyout.Opening event doesn't fire when wired via XAML attribute

because MenuFlyout is not a Control in the visual tree — it's an

AvaloniaObject attached via Button.Flyout. Wire the event in the

constructor instead, where we can directly access the flyout instance.

Use proper ColumnDefinition with pixel width (340, min 280, max 600)

instead of Auto column with Border.Width — GridSplitter cannot resize

Auto columns. Add hover styling and resize cursor to the splitter for

a visible drag handle.

The flyout was being populated via a Button.Click handler, but the

MenuFlyout renders before Click fires. Switch to the flyout's

Opening event so items are populated before the flyout is displayed.