Implement the deconstruction queue

Demolishing a fully-built building now queues it for timed deconstruction
(world.toml deconstruction_time_seconds, default 0.1) running in parallel
with the construction queue, instead of removing it instantly. The partial
refund is credited on completion. A queued building stops operating at once
(belt/tunnel/splitter tiles unregister from the belt subsystem, re-pairing
tunnels) but keeps occupying its tiles. Construction sites are still removed
instantly with the full refund.

Clicking a queued building un-queues it (new CancelDeconstructionCommand);
a demolish drag-box un-queues all covered built buildings when they are all
already queued, otherwise queues the rest. Queued buildings render with the
demolish tint. Implements REQ-BLD-DECON-QUEUE and the updated
REQ-BLD-DEMOLISH / REQ-BLD-DEMOLISH-CLICK / REQ-BLD-DEMOLISH-BOX /
REQ-BLD-TUNNEL-PAIR.

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

src/lib/sim/Building.h

@@ -129,5 +129,10 @@ struct Building
 
     // Module layout for shipyards (REQ-MOD-LAYOUT).
     std::optional<ShipLayoutConfig> shipLayout;
+
+    // True while this building sits in the deconstruction queue (REQ-BLD-DECON-QUEUE).
+    // A queued building stops operating immediately (all tick loops skip it) but keeps
+    // occupying its tiles until its deconstruction completes.
+    bool queuedForDeconstruction = false;
 };