fix(snapshot): per-slice merge + WireSnapshotState type at the wire boundary - #77

The per-slice wire-merge introduced in #77 (d1aa7b9) enumerates every
AppState slice; the announcements slice that landed on this branch
needs the same merge line so the AppState object literal still
satisfies the type. TypeScript catches this by design — that's the
guard the new helper documents.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* feat(announcements): shared slice + settings fields

Adds an announcements slice (items + lastFetched + lastError) wired
into the root reducer alongside existing slices. Settings gets two
new fields, dismissedAnnouncementIds and announcementsMuted, with
events and tests, so the per-banner `×` and the "Hide all" action
can persist across reloads via the existing settings persistence
path.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* feat(announcements): main-process poller + persistence + IPC

Adds AnnouncementsPoller that fetches harness.mikelyons.org/announcements.json
on start and every 6h with a 10s AbortController timeout. Each entry is
validated strictly: id/title/href/publishedAt are required strings,
href must parse as an http(s) URL, and publishedAt must be a parseable
date — malformed entries are dropped individually with a debug-log
line, the rest of the feed is preserved. Network failures dispatch
fetchFailed and stay silent in the UI.

dismissedAnnouncementIds and announcementsMuted persist through the
existing config.json path so dismissals survive a reload. Three IPC
handlers (announcements:refresh / :dismiss / :mute) expose the writes.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* feat(announcements): renderer hook + banner UI

useAnnouncements() exposes the slice; the App-level useMemo filters
expired + dismissed entries, returns null when muted, otherwise picks
the entry with the newest publishedAt. The banner sits below the
update banners using the accent semantic color so it doesn't compete
with update green/info. Title links to href via shell.openExternal;
× dismisses just this id; the ⋯ menu offers "Hide all announcements"
which sets announcementsMuted. Window focus piggybacks an
announcements:refresh alongside the existing PR stale-refresh.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix(announcements): stretch menu wrapper so dropdown clears drag-region

The kebab button's wrapper was sized to the button (~22px), but the
banner row is ~42px tall with py-2.5 padding. items-center on the
row centered the wrapper vertically, leaving the absolute menu's
top edge inside the row — and the row's drag-region captured clicks
on the menu's top ~6px (no-drag isn't reliably inherited by
absolutely-positioned descendants in every Webkit build).

self-stretch + flex items-center stretches the wrapper to the full
row height while keeping the button visually centered, so top-full
now anchors the menu cleanly below the row. Also tagged the menu
container and the menuitem with no-drag as defense in depth.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix(announcements): wire announcements slice into mergeWireSnapshot

The per-slice wire-merge introduced in #77 (d1aa7b9) enumerates every
AppState slice; the announcements slice that landed on this branch
needs the same merge line so the AppState object literal still
satisfies the type. TypeScript catches this by design — that's the
guard the new helper documents.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* chore(site): empty announcements feed before banner ships

The welcome entry was test data for verifying the banner renders
end-to-end during development. Empty the array so the feature ships
with no banner showing by default — future announcements get added
deliberately, not because a placeholder slipped through.

The file stays in place (rather than getting deleted) so the URL
returns valid JSON and the poller's success path runs cleanly
instead of logging a 404 on every refresh.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>