Surface alliance renewal & rejection events in important-events panel (#4354)

## Problem

The important-events notification panel splits events into a prominent
**tier-1** list and a dim, auto-expiring **tier-2** list (capped at the
4 newest entries). Two alliance notifications were landing in tier-2,
making them easy to miss:

- **"X wants to renew your alliance"** (`RENEW_ALLIANCE`) — the core
simulation still sends this when another player requests a renewal, but
it was buried in tier-2, so you couldn't reliably tell whether someone
had asked to renew.
- **"X rejected your alliance"** (`ALLIANCE_REJECTED`) — also tier-2, so
the outcome of a sent request was inconsistent (accepted was prominent,
rejected was not).

## Fix

Add `MessageType.RENEW_ALLIANCE` and `MessageType.ALLIANCE_REJECTED` to
`TIER_1_TYPES` in `EventsDisplay.ts`, so they show prominently alongside
the already-tier-1 `ALLIANCE_ACCEPTED` event.

No core/simulation changes — the messages were already being emitted;
only the client presentation needed fixing. Display styling for both
message types already exists in `Utils.ts`.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

src/client/hud/layers/EventsDisplay.ts

@@ -51,7 +51,9 @@ const TIER_1_TYPES: ReadonlySet<MessageType> = new Set([
   MessageType.NAVAL_INVASION_INBOUND,
   MessageType.ATTACK_REQUEST,
   MessageType.ALLIANCE_ACCEPTED,
+  MessageType.ALLIANCE_REJECTED,
   MessageType.ALLIANCE_BROKEN,
+  MessageType.RENEW_ALLIANCE,
   MessageType.CONQUERED_PLAYER,
   MessageType.CHAT,
   MessageType.DONATION_RECEIVED,