Update documentation for player, inventory, and weapon systems

- Added C++ status updates for player systems (02-player-systems.md) indicating the implementation status of systems 08-11 and their relation to BPC_StateManager.
- Enhanced inventory systems documentation (04-inventory-systems.md) with C++ status for BPC_InventorySystem and DA_ItemData, clarifying their implementation details.
- Updated weapons systems documentation (08-weapons-systems.md) to reflect the C++ implementation status of BPC_DamageReceptionSystem and stubs for hit reaction and shield defense systems.

docs/developer/02-player-systems.md

@@ -2,6 +2,8 @@
 
 **Category Purpose:** These 8 systems form the player character's core simulation layer — health, stamina, stress, movement, hiding, first-person body, camera, and metrics tracking. They cascade: health affects stress, stress affects movement, movement affects camera. All feed into the animation system (ABP_GASP) via event dispatchers.
 
+**C++ Status:** Systems 08-11 have C++ stubs (`Source/PG_Framework/Public/Player/`) providing UCLASS definition, basic variables, and event dispatchers. The Blueprint child provides the full runtime implementation. Systems 12-15 are BP-only. All 8 are referenced by `BPC_StateManager` (130) for gating evaluations.
+
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 ## System Index