Knight fortresses: knight towers, patrols, alarm, claimable knight ground and vaults

- fortress.rs: fortress builder (masonry walls with doors, courtyard, corner towers, vault chambers
  full of mixed treasure, shard chamber, gate of the order as the heart, guards, patrols)
- Knight towers shoot the player's units; creatures tear down knight towers within reach
- Patrols walk their round; guards and patrols that spot an enemy alarm the others nearby
- Imps claim knight ground (slower, not next to fighting heroes); vaults hand over their treasure,
  shard chambers give the shard back; claiming alarms the knights
- Knights tear down the player's bridges near their posts
- Fix: units next to a tower could stop at the tile edge just out of melee reach
- Tests for towers, vault looting, patrols/alarm and bridge tearing

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

lang/en.lang

@@ -415,3 +415,12 @@ treasury.content = Holds {0} worth of {1}
 hud.payday = Payday
 msg.payday_soon = Payday in {0} seconds: your creatures want {1} gold.
 hint.payday_short = There is not enough gold for the coming payday. Unpaid creatures get angry!
+
+# knight fortresses
+msg.enemy_tower_destroyed = A knight {0} has fallen!
+msg.vault_taken = Knight vault taken: {0} worth of treasure is yours.
+msg.shard_taken = A shard of your soul core is back in your hands!
+msg.bridge_torn = The knights have torn down one of your bridges!
+job.tear_bridge = Tearing down a bridge
+job.patrol = On patrol
+job.guard = On guard