Extend the endgame, add more content, make kaos events recur

Balance: an optimal-play simulation showed the game finishing in
under 3 minutes, mostly because torso_beacon + grand_ritual_prep
alone pushed ritualRate to 2.5 — enough to clear the last 50 ritual
points in 20 seconds. Softened those boosts (0.5→0.15, 2→0.35),
raised deepen_ritual's cost curve so it's a real endgame sink instead
of a one-off top-up, and added two new late-game upgrades (sunken
choir, nine filled chairs) between grand_ritual_prep and the win.
Re-simulated: a greedy optimal-play bot now takes ~5 minutes instead
of ~3 and surfaces ~40 distinct events instead of ~30 out of a much
larger pool — real (non-bot) play should run considerably longer.

Content: added 8 new high-dread late-game standard events (gated up
to minDread 400, since nothing previously escalated past 75) and 7
new kaos events, plus one more choice event.

Kaos events no longer get marked as permanently used — they're
chaos-relief flavor, not narrative progression, and a ~24-entry pool
(now 30) was depleting for good over a long game. Standard/chain
events remain single-use.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/engine.test.ts

@@ -136,7 +136,7 @@ describe('deepen_ritual cost scaling', () => {
   it('grows monotonically with each purchase, giving andakt a late-game sink', () => {
     let s = createState();
     s.upgrades.add('grand_ritual_prep');
-    s.ritualRate = 2.5; // baseline after torso_beacon + grand_ritual_prep
+    s.ritualRate = 0.5; // baseline after torso_beacon (0.15) + grand_ritual_prep (0.35)
     s.andakt = 1_000_000;
     s.dread = 1_000_000;