Document carry capacity placeholder

AGRARIAN_DEVELOPMENT_ROADMAP.md

@@ -510,7 +510,11 @@ Target deliverable: A small group can join a server, spawn into one biome, gathe
   state; tools remain inventory items until active hand, worn, backpack, armor,
   weapon, durability, animation, or mesh-attachment rules require replicated and
   persisted slot state.
-- [ ] Add weight or carry capacity placeholder.
+- [x] Add weight or carry capacity placeholder. Locked MVP carry capacity to
+  stack `UnitWeight`, inventory `GetTotalWeight`, character comfort/heavy carry
+  thresholds, strength-scaled movement penalties, and a debug HUD carried
+  weight readout. Later volume, backpack, awkward-object, and hard overload
+  rules should extend this hook.
 - [ ] Add inventory UI.
 - [x] Add replication for inventory changes.
 - [ ] Add persistence for inventory.

Docs/InventoryDataModel.md

@@ -120,6 +120,27 @@ The 0.1.E inventory work should implement these operations on top of the model:
   systems layered on top.
 - UI: read the replicated stack list and send requests back through server RPCs.
 
+## Carry Capacity Placeholder
+
+The 0.1.E MVP carry-capacity placeholder is implemented as a weight-first
+movement penalty, not a hard inventory lock. Each `FAgrarianItemStack` stores
+`UnitWeight`; `UAgrarianInventoryComponent::GetTotalWeight` sums
+`Quantity * UnitWeight`; and `AAgrarianGameCharacter` reads that total through
+`GetCurrentCarryWeight`.
+
+The default comfort and heavy thresholds are `25.0` and `60.0` item-weight
+units. `StrengthMultiplier` scales those thresholds so stronger characters can
+carry more before penalties. Movement remains full speed at or below the
+effective comfort threshold, trends down toward `65%` between comfort and heavy
+loads, and uses a `45%` carry multiplier at or above the heavy threshold. The
+debug HUD shows current carried weight so designers can tune item weights during
+play tests.
+
+This intentionally leaves volume, containers, backpacks, injuries, fatigue,
+awkward-object handling, and hard over-encumbrance rules for later systems.
+Those systems should build on the existing total-weight hook instead of adding a
+parallel inventory burden model.
+
 ## Equipment Slot Decision
 
 Dedicated equipment slots are deferred for the 0.1.E MVP. Current MVP tools,

Docs/TechnicalDesignDocument.md

@@ -130,6 +130,14 @@ or mesh-attachment state. When that need appears, equipment should be added as
 server-authoritative, replicated, persisted slot state rather than as local UI
 selection only.
 
+Carry capacity is active as an MVP placeholder through stack `UnitWeight`,
+inventory `GetTotalWeight`, and character movement penalties. The current
+character uses `25.0` comfort and `60.0` heavy item-weight thresholds, scales
+those thresholds by strength, and exposes current carried weight in the debug
+HUD. Future backpacks, containers, awkward-object rules, and hard overload
+limits should extend this total-weight path rather than creating a second carry
+model.
+
 ## Time And Environment
 
 The MVP gameplay calendar target is:

Scripts/verify_carry_capacity_placeholder.py

@@ -0,0 +1,88 @@
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[1]
+FILES = {
+    "AgrarianTypes.h": ROOT / "Source" / "AgrarianGame" / "AgrarianTypes.h",
+    "AgrarianInventoryComponent.cpp": ROOT / "Source" / "AgrarianGame" / "AgrarianInventoryComponent.cpp",
+    "AgrarianGameCharacter.h": ROOT / "Source" / "AgrarianGame" / "AgrarianGameCharacter.h",
+    "AgrarianGameCharacter.cpp": ROOT / "Source" / "AgrarianGame" / "AgrarianGameCharacter.cpp",
+    "AgrarianDebugHUD.cpp": ROOT / "Source" / "AgrarianGame" / "AgrarianDebugHUD.cpp",
+    "InventoryDataModel.md": ROOT / "Docs" / "InventoryDataModel.md",
+    "TechnicalDesignDocument.md": ROOT / "Docs" / "TechnicalDesignDocument.md",
+    "AGRARIAN_DEVELOPMENT_ROADMAP.md": ROOT / "AGRARIAN_DEVELOPMENT_ROADMAP.md",
+}
+
+EXPECTED = {
+    "AgrarianTypes.h": [
+        "UnitWeight",
+    ],
+    "AgrarianInventoryComponent.cpp": [
+        "UAgrarianInventoryComponent::GetTotalWeight",
+        "Stack.UnitWeight",
+        "Stack.Quantity",
+    ],
+    "AgrarianGameCharacter.h": [
+        "ComfortableCarryWeight = 25.0f",
+        "HeavyCarryWeight = 60.0f",
+        "CalculateCarryWeightMovementMultiplier",
+        "GetCurrentCarryWeight",
+    ],
+    "AgrarianGameCharacter.cpp": [
+        "AAgrarianGameCharacter::GetCurrentCarryWeight",
+        "InventoryComponent->GetTotalWeight()",
+        "CalculateCarryWeightMovementMultiplier()",
+        "AAgrarianGameCharacter::CalculateCarryWeightMovementMultiplier",
+        "StrengthMultiplier",
+        "FVector2D(1.0f, 0.65f)",
+        "return 0.45f",
+    ],
+    "AgrarianDebugHUD.cpp": [
+        "GetCurrentCarryWeight()",
+    ],
+    "InventoryDataModel.md": [
+        "## Carry Capacity Placeholder",
+        "weight-first",
+        "movement penalty",
+        "`UnitWeight`",
+        "`GetTotalWeight`",
+        "`GetCurrentCarryWeight`",
+        "`25.0`",
+        "`60.0`",
+        "`StrengthMultiplier`",
+        "`45%` carry multiplier",
+        "parallel inventory burden model",
+    ],
+    "TechnicalDesignDocument.md": [
+        "Carry capacity is active as an MVP placeholder",
+        "stack `UnitWeight`",
+        "inventory `GetTotalWeight`",
+        "`25.0` comfort and `60.0` heavy",
+        "debug",
+        "HUD",
+    ],
+    "AGRARIAN_DEVELOPMENT_ROADMAP.md": [
+        "[x] Add weight or carry capacity placeholder.",
+        "stack `UnitWeight`",
+        "inventory `GetTotalWeight`",
+        "strength-scaled movement penalties",
+    ],
+}
+
+
+def main():
+    missing = []
+    for label, path in FILES.items():
+        text = path.read_text(encoding="utf-8")
+        for snippet in EXPECTED[label]:
+            if snippet not in text:
+                missing.append(f"{label}: {snippet}")
+
+    if missing:
+        raise RuntimeError("Carry capacity placeholder verification failed: " + "; ".join(missing))
+
+    print("Agrarian carry capacity placeholder verification complete.")
+
+
+if __name__ == "__main__":
+    main()