Implement config-driven unlock groups

Lift unlocking into first-class unlock groups defined in unlocks.toml, so
one defence-station drop can grant a bundle of ships/modules/buildings/
recipes at once (e.g. the salvager module + salvage bay), and buildings
can now be locked at game start and unlocked via a drop.

Config:
- New UnlocksConfig + ConfigLoader::loadUnlocks + validateUnlocks (unknown/
  duplicate/non-assembler grants, unknown requires, empty group all fail load).
- Drop unlock_at_station_level/unlock_requires from ship/module/recipe defs;
  add unlocked_at_start bool to recipes for graph-unreachable base recipes.

Simulation:
- Track awarded groups + per-building unlock state; an item starts unlocked
  iff no group grants it. Rework generateSchematicChoices/applySchematicChoice
  to operate on groups (grant all members at once). Extend state checksum.
- isBuildingUnlocked query; tryPlaceBuilding rejects locked types.

UI:
- Build-menu buttons for locked buildings start hidden, revealed via a new
  UnlockedBuildingsChangedEvent (emitted from GameWorldView's poll loop).
- Schematic choice dialog lists a group's granted items.
- Blueprint placement excludes locked building types (REQ-LOCK-UI-BLUEPRINT).

Data: unlocks.toml (app + test) reproduces the prior per-item gates as
singleton groups and adds salvage_operations (salvager + salvage_bay, lvl 1)
and reprocessing (reprocessing_plant, lvl 2).

Tests: rewrote unlock/config/recipe-schematic/artifact/wave/shipyard tests
for the group model; added UnlockGroupTest. All 443 cases pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Y7N59FsLA5e2kuVdqe4Uhc

src/test/WaveSystemTest.cpp

@@ -305,26 +305,35 @@ TEST_CASE("WaveSystem: push schematic choices have valid ids", "[wave]")
 
     for (const SchematicChoiceOption& opt : choices)
     {
-        bool validId = false;
-        for (const ShipDef& def : sim.getConfig().ships.ships)
+        if (opt.isArtifact) { continue; }
+        bool validGroup = false;
+        for (const UnlockGroupDef& group : sim.getConfig().unlocks.groups)
         {
-            if (def.id == opt.schematicId) { validId = true; break; }
+            if (group.id == opt.unlockGroupId) { validGroup = true; break; }
         }
-        if (!validId)
+        REQUIRE(validGroup);
+        // Every granted item must resolve to a defined ship/module/building/recipe.
+        for (const GrantedSchematic& grant : opt.grantedItems)
         {
+            bool validId = false;
+            for (const ShipDef& def : sim.getConfig().ships.ships)
+            {
+                if (def.id == grant.id) { validId = true; break; }
+            }
             for (const ModuleDef& def : sim.getConfig().modules.modules)
             {
-                if (def.id == opt.schematicId) { validId = true; break; }
+                if (def.id == grant.id) { validId = true; break; }
+            }
+            for (const BuildingDef& def : sim.getConfig().buildings.buildings)
+            {
+                if (def.id == grant.id) { validId = true; break; }
             }
-        }
-        if (!validId)
-        {
             for (const RecipeDef& def : sim.getConfig().recipes.recipes)
             {
-                if (def.id == opt.schematicId) { validId = true; break; }
+                if (def.id == grant.id) { validId = true; break; }
             }
+            REQUIRE(validId);
         }
-        REQUIRE(validId);
     }
 }
 
@@ -343,7 +352,7 @@ TEST_CASE("WaveSystem: schematic choices have no duplicates", "[wave]")
     std::set<std::string> ids;
     for (const SchematicChoiceOption& opt : choices)
     {
-        ids.insert(opt.schematicId);
+        ids.insert(opt.isArtifact ? std::string("<artifact>") : opt.unlockGroupId);
     }
     REQUIRE(ids.size() == choices.size());
 }