target single-building transfers by hovering, not by footprint coincidence

Coincidence required the ghost's anchor to land exactly on the target's
anchor, so on a 2x2 assembler three of its four tiles read as an ordinary
overlap and went red: you had to find the top-left tile before the copy
gesture would fire. A single-building blueprint now finds its target by
hit-testing the cursor instead -- any body tile, any facing -- and its ghost
snaps onto the target so it shows what the click will act on.

A constellation is unchanged: it is placed as a layout, so its ghosts stay
where the blueprint puts them and still need coincidence plus a matching
rotation. The old "single-building blueprints ignore target rotation"
carve-out is gone, subsumed by hovering.

blueprintHoldsOneBuilding becomes std::optional<QPoint> hoverTile, which
carries both facts in one parameter: set means "single-building blueprint,
cursor here". BlueprintGhostResolved gains ghostAnchor/ghostRotation so the
snap comes out of the classifier both callers already share, rather than
the renderer working it out separately.

Note the shipyard, which I had cited as the motivating case, is not one: its
mask needs A cells on asteroid and S cells in space, and the asteroid edge
is vertical, so a rotated shipyard can never be placed at all. Rotation was
never the real problem here; alignment was.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JcReq7hVk4KUPhTDKWAG7K

src/lib/sim/PlacementRules.h

@@ -79,14 +79,24 @@ struct BlueprintGhostResolved
 {
     BlueprintGhostAction      action;
     std::optional<BuildingId> targetId;  // set for CompatibleOverlap and Transfer
+    // Where the ghost belongs on screen. The queried anchor and rotation, except at a
+    // hovered transfer target, where the ghost snaps onto the target so it shows what the
+    // click will act on (REQ-UI-BLUEPRINT-TRANSFER).
+    QPoint                    ghostAnchor;
+    Rotation                  ghostRotation;
 };
 
 // Classifies one ghost of a blueprint against the current factory state
-// (REQ-UI-BLUEPRINT-OVERLAP, REQ-UI-BLUEPRINT-TRANSFER). `blueprintHoldsOneBuilding`
-// only widens the transfer rule to differently-facing targets; a same-facing target
-// transfers whatever the blueprint's size. It is the blueprint's stored size, counted
-// before locked types are dropped, so the gesture does not change behavior as the player
-// unlocks things.
+// (REQ-UI-BLUEPRINT-OVERLAP, REQ-UI-BLUEPRINT-TRANSFER).
+//
+// `hoverTile` is set only for a blueprint holding exactly one building, and is then the
+// tile under the cursor. That gesture is a copying tool rather than a layout, so it finds
+// its transfer target by hit-testing the cursor instead of by footprint coincidence --
+// without which a Shipyard could never be targeted at a different facing, its 4x2
+// footprint covering entirely different tiles once rotated. Pass nullopt for a
+// constellation, whose ghosts are judged purely by where the blueprint puts them. The
+// size is read from the blueprint as stored, before locked types are dropped, so the
+// gesture does not change behavior as the player unlocks things.
 //
 // Shared by the ghost coloring and the click path so a preview cannot disagree with what
 // the click then does -- the same reason resolveBeltDragPath is shared.
@@ -94,7 +104,7 @@ BlueprintGhostResolved resolveBlueprintGhost(const FactoryState& state,
                                              const GameConfig& config,
                                              BuildingType type, QPoint anchor,
                                              Rotation rotation,
-                                             bool blueprintHoldsOneBuilding);
+                                             std::optional<QPoint> hoverTile);
 
 // What a belt drag would do to one tile of its path (REQ-BLD-BELT-DRAG).
 enum class BeltTileAction