test: de-duplication + malformed-locale assertions

§19 verifies sources={c, c} is de-duplicated (have=1, not 2).
§20 verifies {sink=c} without sources raises a loud-error
attributing crafting + sources.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

init.lua

@@ -1,5 +1,7 @@
--- lib-core.crafting-test — Phase C.1
--- 12 assertions: 5 registry (define_recipe + list + get) + 7 discovery/match/craft.
+-- lib-core.crafting-test — Phase C.1 + D.0
+-- 20 assertions: 12 base (registry + discovery/match/craft), 6 locale-API
+-- (Form-2 happy + greedy-drain + aggregate + Loud-Errors), 2 silent-fail
+-- regressions (duplicate-sources de-dup + malformed-locale loud-error).
 -- Pattern follows P.2.4 Test-Module-Pattern; TAP output via engine.test.*
 
 local composition = require("lib-core.composition")
@@ -531,6 +533,73 @@ function M.run_tests(ctx)
                  and string.find(err18, "sink")     ~= nil
                  and string.find(err18, "nil")      ~= nil,
         "18. Loud-Error: locale.sink=nil → error mentions 'crafting', 'sink', 'nil'")
+
+    -- ================================================================
+    -- §19: Duplicate sources are de-duplicated.
+    --      Single container with 1 rock; pass {c, c} as sources.
+    --      count_by_template must NOT double-count → can_craft for a
+    --      recipe needing 2 rocks reports have=1 (not 2).
+    -- ================================================================
+    local c_19 = setup_container{
+        { template = "craft_test.rock", count = 1 },
+    }
+    composition.define_template{
+        id         = "craft_test.rock_pile_19",
+        properties = {
+            stack_mode  = "individual",
+            sprite_path = "sprites/pile.png",
+            position    = {x = 0, y = 0},
+        },
+        tags = {"renderable", "item"},
+    }
+    crafting.define_recipe{
+        id     = "r2rocks_19",
+        inputs = { { template = "craft_test.rock", count = 2 } },
+        output = { template = "craft_test.rock_pile_19", count = 1 },
+    }
+    local cc19 = crafting.can_craft("r2rocks_19",
+        { sources = {c_19, c_19}, sink = c_19 }, {})
+    local missing_match_19 = false
+    if cc19.missing then
+        for _, m in ipairs(cc19.missing) do
+            if m.template == "craft_test.rock"
+                    and m.needed == 2 and m.have == 1 then
+                missing_match_19 = true; break
+            end
+        end
+    end
+    T.assert(cc19.ok == false and cc19.error == "missing_inputs"
+                 and missing_match_19,
+        "19. Duplicate sources de-duplicated: sources={c,c} with 1 rock reports have=1 (not 2)")
+
+    -- ================================================================
+    -- §20: Loud-Error — Form-2 table without sources field.
+    --      Caller typo passes {sink=c} without sources. resolve_locale
+    --      must loud-error attributing crafting + sources, not silently
+    --      fall through to the Form-1 bw-compat shim (which would then
+    --      crash deep inside inventory-list).
+    -- ================================================================
+    local c_20 = setup_container{}
+    composition.define_template{
+        id         = "craft_test.x_20",
+        properties = {
+            stack_mode  = "individual",
+            sprite_path = "sprites/x.png",
+            position    = {x = 0, y = 0},
+        },
+        tags = {"renderable", "item"},
+    }
+    crafting.define_recipe{
+        id     = "rp_20",
+        inputs = { { template = "craft_test.rock", count = 1 } },
+        output = { template = "craft_test.x_20", count = 1 },
+    }
+    local malformed_20 = { sink = c_20 }
+    local ok20, err20 = pcall(crafting.craft, "rp_20", malformed_20, {})
+    T.assert(not ok20 and type(err20) == "string"
+                 and string.find(err20, "crafting") ~= nil
+                 and string.find(err20, "sources")  ~= nil,
+        "20. Loud-Error: locale table without 'sources' field → error mentions 'crafting' and 'sources'")
 end
 
 return M