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

README.md

@@ -21,8 +21,9 @@ from per-ship seeds) — the probability is *yours*, not the universe's.
 
 - You start docked. Buy what a planet produces cheap, sell where it's consumed.
 - Sidebar: navigation, market (when docked), cargo, intel, log. Space = pause,
-  Tab = map/system view. Click planets/gates/systems to move; click systems on
-  the map for price intel — note the age tag, old news lies.
+  Tab = map/system view. Move by clicking planets and gate diamonds in the
+  system view, or use the Navigation buttons. Click systems on the galaxy map
+  for price intel — note the age tag, old news lies.
 - Lanes are tinted by pirate danger. Dangerous shortcuts are profitable until
   they aren't.
 - Orange smears on the map are ships you've met: where they probably are now.