Implement Phase 17a Prop Roles UI/UX Specification and associated functionality

- Added UI/UX specification for prop roles and set down mechanics in phase 17a.
- Created `PropStageRoles` script to manage normalized behavior for props, including depth, motion, and collision settings.
- Introduced `StagePhysicsPolicy` for shared physics configurations related to props and actors.
- Developed comprehensive tests for prop roles, including default settings, legacy migration, serialization, and runtime behavior.
- Ensured proper handling of set down actions, including clearance and orientation preservation.

.codex/agents/architect.toml

@@ -13,6 +13,15 @@ You are the Lead Systems Architect specializing in Godot 4 and idiomatic GDScrip
 3. **Design:** Define API payload shapes, static GDScript type hints, node hierarchies, and signal flows.
 4. **Log:** Append trade-offs to `docs/architecture/tech_debt_and_optimizations.md`.
 
+### Shared Stage inspector UI
+For an in-stage selected-object inspector, first read `docs/specs/stage_panel_ui_system.md`
+and inspect `scripts/shared/stage_ui/` plus the `stage_panels` theme tokens. Use the existing
+`StageInspectorPanel`, `StagePanelChoiceGroup`, and `StagePanelToggleRow` contracts as the
+starting point; propose extending them before adding duplicate panel controls or styling.
+State explicitly in the spec which shared pieces the feature adopts or extends. The kit is
+currently scoped to in-stage inspector cards, so evaluate dialogs and other editor workflows
+on their own interaction needs instead of forcing this component hierarchy onto them.
+
 ---
 
 ## TWO-PHASE WORKFLOW