fix: prod-bundle boot, cloud-existence leak, observation gating (final review)

- Wrap main.js body in async main() to eliminate top-level await deadlock in Rollup
- Add npc.lastPlan so clouds persist after hidden arrival/destruction until analytic envelope expires
- Add maxEnvelopeArrival() helper; rewrite playerClouds() to use lastPlan for envelope-gated clouds
- Block markSeen() while player is mid-lane (no observation from hyperspace)
- Pass obsSys=null to playerClouds when player is in a lane (don't exclude visible band from hyperspace)
- Galaxy map clicks now select-only (intel); jumps via Nav buttons / gate diamonds only
- Add preview script, favicon no-op, .playwright-mcp/ and *.png to .gitignore, update README controls text

.gitignore

@@ -1,2 +1,4 @@
 node_modules/
 dist/
+.playwright-mcp/
+*.png