Rename Demolish to Deconstruct; add build button grid icons

Rename the Demolish* terminology to Deconstruct* across the simulation,
events, UI, tests, and docs (DemolishCommand and the DemolishMode* events
become their Deconstruct* equivalents), aligning with the deconstruction
queue at HEAD.

Add per-building SVG icons for the build button grid (REQ-UI-BUILD-GRID):
one color-chip icon per placeable building under data/icons/buildings,
loaded from disk at runtime and rendered with QtSvg onto each build button.
An unaffordable building's button shows a grey-recolored variant via a
QIcon Disabled-mode pixmap (REQ-UI-BUILD-DISABLED). Adds the Qt5::Svg
dependency and deploys Qt5Svg.dll.

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

docs/replay_design.md

@@ -55,7 +55,7 @@ data, not the UI gesture. Example: placing a miner records
 One command per sim-mutating operation (the complete mutation surface):
 
 - `PlaceBuilding`
-- `Demolish`
+- `Deconstruct`
 - `RotateInPlace`
 - `SetRecipe`
 - `SetShipLayout`
@@ -125,7 +125,7 @@ the only way production code can reach them is `apply(command)`.
 > `BeltSystem` directly, and every production `buildings()`/`belts()` call is a const query.
 > So:
 >
-> - `Simulation::tryPlaceBuilding`, `demolish`, and `applySchematicChoice` are **private**.
+> - `Simulation::tryPlaceBuilding`, `deconstruct`, and `applySchematicChoice` are **private**.
 > - The mutable subsystem accessors are private and renamed `buildingsMutable()` /
 >   `beltsMutable()`; only `const BuildingSystem& buildings() const` / `belts() const` are
 >   public (queries). UI query sites bind to the const overload unchanged.
@@ -377,7 +377,7 @@ The whole feature rests on a deterministic sim, so prove that before building on
 
 Reshape mutations to flow through one path; behaviour unchanged.
 
-- Defined `Command` base + derived types (`PlaceBuilding`, `Demolish`, `RotateInPlace`,
+- Defined `Command` base + derived types (`PlaceBuilding`, `Deconstruct`, `RotateInPlace`,
   `SetRecipe`, `SetShipLayout`, `SetSiteSplitterFilters`, `SetSplitterFilters`,
   `ClearBeltTiles`, `ApplySchematicChoice`, `Reset`) in `lib`, each with a `playerId` (always 0
   now). `PlaceBuilding` is atomic (carries optional config — see the refinement note above).