feat(vagrant): Tab-Toggle inventory panel + right-click context menu

- lib-core.panel and lib-core.inventory-list-display added to deps (v0.1.0 each)
- backpack-widget created in M.init with label-resolver returning "Rock"
- Drop action registered: removes from backpack, relocates to player position,
  re-registers pickup trigger
- Inspect action registered: prints reg_id via engine.print
- M.update: panel.update(dt) + is_pausing() early-return added after
  quit_to_launcher check
- interaction.update wrapped in panel.is_open() guard to block world triggers
  while panel is visible
- M.draw: panel.render() added at z-top after CI traces
- Q-drop (LIFO quick-drop via Q key) unchanged and parallel to panel Drop action

init.lua

@@ -1,4 +1,4 @@
--- sporel-module-vagrant-skeleton v0.8.0
+-- sporel-module-vagrant-skeleton v0.9.0
 -- Sprite-mode test-chamber: 13-bone humanoid puppet + sprite-tilemap +
 -- hardcoded furniture. Subterrain-style puppet control model:
 -- multi-look-target (aim/soft), slerp body rotation, hip-static legs,
@@ -22,6 +22,11 @@
 -- position. engine.print shows inventory count + item-IDs after each
 -- add/remove. Tree-check (CI-gated) verifies child placement in
 -- composition tree.
+--
+-- v0.9.0: Inventory panel UI wired in. Tab toggles a panel overlay
+-- showing backpack contents. Right-click on an item row opens a context
+-- menu with Drop and Inspect actions. Q-drop (LIFO quick-drop) remains
+-- available in parallel.
 
 local input       = require("lib-core.input")
 local camera      = require("lib-core.camera")
@@ -32,6 +37,8 @@ local interaction = require("lib-core.interaction")
 local composition = require("lib-core.composition")
 local actor       = require("lib-core.actor")
 local inventory   = require("lib-core.inventory-list")
+local panel       = require("lib-core.panel")
+local inv_display = require("lib-core.inventory-list-display")
 
 local M = {}
 
@@ -389,6 +396,43 @@ function M.init(ctx)
     register_pickup(state.rock)
     if CI_FRAME_PERF then engine.print("vagrant: rock_spawned") end
 
+    -- Inventory-UI Setup
+    panel.set_theme{ panel_width_frac = 0.4, font_size_title = 20 }
+
+    local backpack_widget = inv_display.create(state.backpack, {
+        title         = "Backpack",
+        widget_id     = "backpack",
+        pause_on_open = false,
+    })
+
+    -- Module-side label-resolver (display lib's default returns "Item").
+    -- Vagrant currently has one item template (rock); hardcoded for v0.9.
+    inv_display.set_label_resolver(backpack_widget, function(item)
+        return "Rock"
+    end)
+
+    -- Drop action: knows world-reparenting + player position
+    inv_display.register_action(backpack_widget, "Drop", function(item, c)
+        inventory.remove(state.backpack, item)
+        local px = state.actor:get_property("position.x")
+        local py = state.actor:get_property("position.y")
+        item:set_property("position.x", px + 30)
+        item:set_property("position.y", py)
+        register_pickup(item)
+        c.close_menu()
+        if CI_FRAME_PERF then engine.print("vagrant: event=drop_via_menu") end
+    end)
+
+    -- Inspect action: dumps reg_id to console
+    inv_display.register_action(backpack_widget, "Inspect", function(item, c)
+        engine.print(string.format("vagrant: inspect: reg_id=%s",
+            tostring(item:get_property("composition.reg_id"))))
+        c.close_menu()
+    end)
+
+    panel.register("backpack", backpack_widget)
+    panel.bind_default_trigger("tab", "backpack")
+
     -- Input bindings.
     input.bind("walk_left",  { "a" })
     input.bind("walk_right", { "d" })
@@ -420,6 +464,10 @@ function M.update(ctx, dt)
         return
     end
 
+    -- Inventory panel input handling
+    panel.update(dt)
+    if panel.is_pausing() then return end
+
     -- Drop: Q pops the most-recently-added item from backpack, relocates
     -- it to world at player position + 30px right offset, and re-registers
     -- a pickup-trigger. inventory.remove restores the renderable tag.
@@ -436,9 +484,9 @@ function M.update(ctx, dt)
 
             -- Inventory inspection trace (unconditional — user-facing demo output).
             local count = inventory.count(state.backpack)
-            local items = inventory.contents(state.backpack)
+            local remaining_items = inventory.contents(state.backpack)   -- re-read post-remove
             local ids = {}
-            for _, it in ipairs(items) do
+            for _, it in ipairs(remaining_items) do
                 table.insert(ids, tostring(it:get_property("composition.reg_id")))
             end
             engine.print(string.format("vagrant: backpack count=%d items=[%s]",
@@ -525,7 +573,9 @@ function M.update(ctx, dt)
 
     -- Interaction: dispatches the nearest matching proximity-trigger when
     -- 'interact' was pressed this frame. Uses actor.position as anchor.
-    interaction.update(actor.position(state.actor))
+    if not panel.is_open() then
+        interaction.update(actor.position(state.actor))
+    end
 
     -- Camera follows actor position each frame.
     camera.set_target(actor.position(state.actor))
@@ -572,6 +622,8 @@ function M.draw(ctx)
             ci_sprite_traced = true
         end
     end
+    -- Inventory panel overlay (z-top: drawn after all world content).
+    panel.render()
 end
 
 -- Engine lifecycle globals (engine looks up by name; module-table is bridged).