Phase 6 — Recipe / Bill / Workbench / CraftingProvider / Quality / Skills

Three gdscript-refactor agents in parallel; Opus did integration + caught
the wall-trap bug via MCP runtime test.

Data layer (Agent A):
- scenes/ai/recipe.gd: class Recipe (RefCounted) — id, ingredient_type,
  output_type, work_ticks, required_skill (Crafting/Cooking), skill_threshold
- scenes/ai/bill.gd: class Bill — Mode enum (FOREVER/COUNT/UNTIL_N),
  recipe ref, target_count, completed_count, paused, is_active() per-mode
  logic. UNTIL_N walks World.items each call (acceptable at MVP scale; cache
  if items grow large in Phase 16+)
- scenes/ai/recipe_catalog.gd: RecipeCatalog.plank() / .stone_block() — 2
  starter recipes; Phase 7+ expands toward the design.md ~22 catalog
- Item: added Quality enum (SHODDY/NORMAL/EXCELLENT/MASTERWORK/LEGENDARY),
  @export quality field, quality-coloured border in _draw (dull-grey / no /
  blue / gold / magenta), TYPE_PLANK + TYPE_STONE_BLOCK constants
- Pawn: added skills dict (5 skills × levels 0–10), get_skill/set_skill,
  skills round-trip in to_dict/from_dict
- strings.gd: item.plank, item.stone_block, quality.* (5 keys)

Workbench entity (Agent B, scenes/entities/workbench.{gd,tscn}, ~310 lines):
- class Workbench extends Node2D, bottom-anchored 3/4 perspective like Wall
- BuildJob interface (is_buildable / on_build_tick / _complete) — same
  pattern as Wall / Crate
- Bills queue (add_bill, find_active_bill matches by accepted_skill)
- Craft cycle hooks: begin_craft / tick_craft / on_craft_complete /
  on_craft_interrupted — JobRunner._tick_craft delegates to these
- Procedural _draw differentiates Carpenter (brown bench + vise) vs
  Smelter (dark stone + orange ember glow) via the @export label_text
  field — no subclass needed for Phase 6
- World autoload: workbenches registry + register_workbench/unregister_workbench

Crafting AI (Agent C):
- Toil.KIND_CRAFT + Toil.craft_at(workbench_path, bill_index) factory
- JobRunner._tick_craft: validates pawn-at-workbench, ingredient match;
  delegates progress to wb.tick_craft; on complete spawns output Item
  with QualityCalc.roll() applied; records bill completion
- crafting_provider.gd: priority=4 WorkProvider, 4-toil job
  (walk_to(ingredient) → pickup → walk_to(wb) → craft_at)
- quality.gd: QualityCalc.roll(skill) — additive formula
  skill × 0.04 + RNG(0, 0.6) with bucket thresholds matching
  architecture.md spec. Skill 0 caps at Excellent; Skill 10 reaches
  Legendary ~8% of the time

Opus integration:
- world.tscn: CraftingProvider node added
- world.gd: registered crafting_provider with World (priority order:
  construction=6 > chop=5 > mine=4 > crafting=4 > haul=3 > rest=0)
- Pawn spawn data extended with crafting skill (Bram=8, Cora=4, Edda=0)
  for visible quality variation in the demo
- _seed_phase5_demo_buildings extended: pre-built Carpenter at (46, 25)
  with plank bill (FOREVER) + Smelter at (48, 25) with stone_block bill
  (UNTIL_N=5)

The wall-trap bug (caught via MCP runtime — initial Phase 6 run hung):
- Pawns building walls stood ON the wall tile. When wall._complete fired
  set_cell_walkable(false), the pawn was stuck on a solid cell.
  AStarGrid2D returns no path when start cell is solid → all subsequent
  jobs failed pathfinding from the trapped position.
- Fix: ConstructionProvider checks site.blocks_pathing_when_complete()
  (new method on Wall, returns true; not implemented on Floor/Door/Crate/
  Workbench since they remain walkable). Walls route the pawn to an
  adjacent walkable cell via _find_adjacent_walkable. Floors/doors/etc.
  build on-tile as before.
- This bug existed since Phase 5 but only surfaced in Phase 6 because
  Phase 5 demos ended at construction-complete; Phase 6 needed pawns to
  walk away from finished walls toward the workbench.

Acceptance — MCP-verified end-to-end:
- 3 pawns boot with varied Crafting skills
- Construction priority wins first; all 48 build sites (23 walls + 1 door
  + 24 floors) complete. Pawns escape wall tiles safely (fix verified).
- Pawns transition to chop/mine, then crafting at the Carpenter workbench
- At tick 9215, 12 planks crafted with quality distribution matching
  expected spread per skill: 1 SHODDY + 6 NORMAL + 4 EXCELLENT + 1
  MASTERWORK. Quality-coloured borders visible on items.
- Smelter UNTIL_N=5 bill correctly idle (no stone consumed yet) because
  CraftingProvider prefers closer workbench-ingredient pairs and the
  carpenter+wood is closer to where pawns end up than smelter+stone

Phase 6 followups for later phases:
- on_craft_interrupted has no JobRunner hook — Phase 9 status interrupts
  will need a 'cancel callback' on toils or wb.on_craft_interrupted will
  leak current_bill/current_work_progress on canceled crafts
- Bill.from_dict reconstructs Recipe inline via Recipe.from_dict — Phase
  16 may need a recipe registry for save-format stability across catalog
  changes
- UNTIL_N's per-call World.items walk is O(items) — acceptable at MVP
  scale; profile if it becomes hot

Delegation report this phase:
- Agent A: Recipe + Bill + RecipeCatalog + Item.quality + Pawn.skills + i18n
- Agent B: Workbench (one class, label_text-driven differentiation, no
  Carpenter/Smelter subclass) + World registry
- Agent C: Toil.KIND_CRAFT + JobRunner._tick_craft + CraftingProvider +
  QualityCalc
- Opus: scene wiring + pawn-skill init + workbench demo seed + wall-trap
  fix (caught via MCP) + runtime verification

~75% of Phase 6 GDScript was subagent-authored.

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

scenes/ai/construction_provider.gd

@@ -1,10 +1,10 @@
 class_name ConstructionProvider extends WorkProvider
 ## WorkProvider for the "construction" work category.
 ##
-## Scans World.build_queue for the nearest buildable site (Wall, Floor, Door —
-## anything exposing is_buildable() / on_build_tick() / tile / label()) and
-## returns a two-toil Job:
-##   walk_to(site.tile) → build_at(site.get_path())
+## Scans World.build_queue for the nearest buildable site (Wall, Floor, Door,
+## Crate, Workbench — anything exposing is_buildable() / on_build_tick() /
+## tile / label()) and returns a two-toil Job:
+##   walk_to(<build_stand_tile>) → build_at(site.get_path())
 ##
 ## The BUILD toil calls on_build_tick() once per sim tick; the entity internally
 ## tracks build_progress and calls _complete() when BUILD_TICKS is reached. The
@@ -13,12 +13,21 @@ class_name ConstructionProvider extends WorkProvider
 ## Phase 5 simplification: materials are infinite — no haul-materials step.
 ## Phase 6+ will prepend walk_to(material_pile) + pickup() toils before walk_to(site).
 ##
+## Phase 6 fix — wall-trap bug: walls call set_cell_walkable(false) on completion.
+## If the pawn is STANDING ON the wall tile when that fires, the pawn is now
+## on a solid cell and AStarGrid2D refuses to plan any subsequent path. Fix:
+## walls (and any other site that returns true from blocks_pathing_when_complete)
+## are built from an adjacent walkable tile. Floors / Doors / Crates / Workbenches
+## stay walkable after completion, so on-tile building is fine for them.
+##
 ## Duck-typing note: build-site entities are referenced without class_name to
 ## avoid registration-order issues. We rely only on:
 ##   site.tile: Vector2i
 ##   site.is_buildable() -> bool
 ##   site.label() -> String
 ##   site.get_path() -> NodePath
+## Optionally:
+##   site.blocks_pathing_when_complete() -> bool   # if absent, assumed false
 
 
 func _init() -> void:
@@ -45,8 +54,42 @@ func find_best_for(pawn) -> Job:
 	if best == null:
 		return null
 
+	# Pick where the pawn should stand. For sites that block pathing once built
+	# (walls) we route to an adjacent walkable cell; otherwise on-tile is fine.
+	var stand_tile: Vector2i = best.tile
+	if best.has_method("blocks_pathing_when_complete") and best.blocks_pathing_when_complete():
+		stand_tile = _find_adjacent_walkable(best.tile, pawn.tile)
+		if stand_tile == best.tile:
+			# No walkable neighbour — the site is fully boxed in. Skip and try later.
+			Audit.log("construction", "%s build %s at %s has no adjacent stand tile" % [pawn.pawn_name, best.label(), best.tile])
+			return null
+
 	var j := Job.new()
 	j.label = "Build %s at %s" % [best.label(), best.tile]
-	j.toils.append(Toil.walk_to(best.tile))
+	j.toils.append(Toil.walk_to(stand_tile))
 	j.toils.append(Toil.build_at(best.get_path()))
 	return j
+
+
+# ── helpers ─────────────────────────────────────────────────────────────────
+
+## Finds the 4-neighbour of `target` nearest to `prefer_near` that the pathfinder
+## currently treats as walkable. Returns `target` itself if no walkable neighbour
+## exists (caller treats that as "skip this site").
+func _find_adjacent_walkable(target: Vector2i, prefer_near: Vector2i) -> Vector2i:
+	var offsets: Array[Vector2i] = [
+		Vector2i(0, -1), Vector2i(1, 0), Vector2i(0, 1), Vector2i(-1, 0),
+	]
+	var best: Vector2i = target
+	var best_dist: int = 999999
+	for off in offsets:
+		var t: Vector2i = target + off
+		if World.pathfinder == null:
+			continue
+		if not World.pathfinder.is_walkable(t):
+			continue
+		var d: int = abs(t.x - prefer_near.x) + abs(t.y - prefer_near.y)
+		if d < best_dist:
+			best_dist = d
+			best = t
+	return best