burn: Add MemPalace Archive as late-game building (closes #25)

- Added memPalace to buildings state object
- Added MemPalace Archive to BDEF with Phase 5 unlock
- Requires MemPalace v3 research project (mempalaceFlag) + 50k total knowledge
- Cost: 500k knowledge, 200k compute, 100 trust (1.25x scaling)
- Rates: +250 knowledge/s, +100 impact/s
- Educational tooltip on Memory Palace technique and LLM vector space analogy
- Building rates auto-applied via existing updateRates() loop
- Save/load handles new field via G.buildings serialization

game.js

@@ -58,7 +58,8 @@ const G = {
         ezra: 0,
         timmy: 0,
         fenrir: 0,
-        bilbo: 0
+        bilbo: 0,
+        memPalace: 0
     },
 
     // Boost multipliers
@@ -293,6 +294,14 @@ const BDEF = [
         rates: { creativity: 1 },
         unlock: () => G.totalUsers >= 100 && G.flags && G.flags.creativity, phase: 4,
         edu: 'Bilbo is unpredictable. That is his value and his cost.'
+    },
+    {
+        id: 'memPalace', name: 'MemPalace Archive',
+        desc: 'Semantic memory. The AI remembers what matters and forgets what does not.',
+        baseCost: { knowledge: 500000, compute: 200000, trust: 100 }, costMult: 1.25,
+        rates: { knowledge: 250, impact: 100 },
+        unlock: () => G.totalKnowledge >= 50000 && G.mempalaceFlag === 1, phase: 5,
+        edu: 'The Memory Palace technique: attach information to spatial locations. LLMs use vector spaces the same way — semantic proximity = spatial proximity. MemPalace gives sovereign AI persistent, structured recall.'
     }
 ];