tools/epro2/kicad: PCB Phase-2 — POUR → (zone), CoreBoard unconnected -43%

Phase-1 left 75-358 unconnected_items per board (DRC), dominated by
GND/AGND/POWER nets that EPRO2 routes through copper pour, not discrete
traces. Phase-2 lands those:

  - pcb_writer._decode_zone_path handles the three POUR.path encodings
    seen in ESP-VoCat: rectangle (['R', x, y, w, h, ...]), circle
    (['CIRCLE', cx, cy, r]) approximated as a 36-segment polygon, and
    polyline (numeric pairs with 'L'/'ARC' verb tokens).
  - Each POUR on a copper layer turns into a (zone (polygon ...) ...)
    block plus a (filled_polygon ...) that mirrors the boundary.

Why mirror, not auto-fill: kicad-cli pcb drc does NOT run the zone
filler before checking — only the KiCad GUI does. Without a
pre-computed (filled_polygon ...), DRC sees zones as empty regions and
reports the entire net as unconnected. Mirroring the boundary as the
fill is "connectivity-correct, clearance-imprecise" — KiCad users can
still hit Edit > Fill Zones to refine thermals and pad clearances. We
chose this over reading EPRO2's POURED.pourFill (the editor's own
post-fill polygons) because POURED paths use ARC tokens we'd need to
fully decode, and the user-drawn POUR boundary is already the
authoritative "intended copper" region.

ESP-VoCat DRC totals: 883 → 730 unconnected_items (-17% project-wide).
CoreBoard, the 4-layer board with the most pour coverage, drops 358 →
205 (-43%). Other boards see no movement because their unconnected
items are non-pour issues — pads outside the user-drawn POUR
rectangle, or internal $1N nets via vias on the wrong net (separate
problem, separate fix).

65 → 68 unit tests pass.

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

tools/epro2/kicad/pcb_writer.py

@@ -80,6 +80,7 @@ class WriteStats:
     segments: int = 0
     vias: int = 0
     edge_cuts: int = 0
+    zones: int = 0
     skipped: int = 0
 
 
@@ -193,6 +194,79 @@ def _is_copper(layer_name: str | None) -> bool:
     return bool(layer_name) and (layer_name.endswith(".Cu"))
 
 
+def _decode_zone_path(
+    raw,
+    *,
+    origin_mm: tuple[float, float],
+    circle_segments: int = 36,
+) -> list[tuple[float, float]]:
+    """EPRO2 POUR.path → list of (x_mm, y_mm) outer-boundary points.
+
+    Three encodings observed in the wild (counts on ESP-VoCat: R 12 / CIRCLE
+    4 / polyline 3). All are wrapped in an extra outer list, i.e.
+    ``path = [<one_shape>]``.
+
+      - rectangle: ``['R', x, y, w, h, r1, r2]`` — corner-radii ignored
+      - circle   : ``['CIRCLE', cx, cy, radius]`` — sampled to N segments
+      - polyline : ``[x1, y1, 'L', x2, y2, ...]``
+    """
+    ox, oy = origin_mm
+    if not isinstance(raw, list) or not raw:
+        return []
+    shape = raw[0]
+    if not isinstance(shape, list) or not shape:
+        return []
+    head = shape[0]
+    if isinstance(head, str) and head.upper() == "R":
+        if len(shape) < 5:
+            return []
+        try:
+            x = float(shape[1]); y = float(shape[2])
+            w = float(shape[3]); h = float(shape[4])
+        except (TypeError, ValueError):
+            return []
+        x0 = ox + x * MIL_TO_MM
+        y0 = oy + y * MIL_TO_MM
+        x1 = x0 + w * MIL_TO_MM
+        y1 = y0 + h * MIL_TO_MM
+        return [(x0, y0), (x1, y0), (x1, y1), (x0, y1)]
+    if isinstance(head, str) and head.upper() == "CIRCLE":
+        if len(shape) < 4:
+            return []
+        try:
+            cx = float(shape[1]); cy = float(shape[2]); r = float(shape[3])
+        except (TypeError, ValueError):
+            return []
+        cx_mm = ox + cx * MIL_TO_MM
+        cy_mm = oy + cy * MIL_TO_MM
+        r_mm = r * MIL_TO_MM
+        return [
+            (cx_mm + r_mm * math.cos(2 * math.pi * i / circle_segments),
+             cy_mm + r_mm * math.sin(2 * math.pi * i / circle_segments))
+            for i in range(circle_segments)
+        ]
+    # Polyline: walk numeric pairs, skip 'L'/'ARC' tokens (ARC chord-approx).
+    pts: list[tuple[float, float]] = []
+    i = 0
+    while i < len(shape):
+        tok = shape[i]
+        if isinstance(tok, str):
+            if tok.upper() == "ARC":
+                # Skip [radius, endX, endY] params; chord approximation drops
+                # arc curvature but keeps the polygon closed enough for fill.
+                i += 4 if len(shape) >= i + 4 else 1
+                continue
+            i += 1
+            continue
+        try:
+            x = float(shape[i]); y = float(shape[i + 1])
+            pts.append((ox + x * MIL_TO_MM, oy + y * MIL_TO_MM))
+            i += 2
+        except (TypeError, ValueError, IndexError):
+            i += 1
+    return pts
+
+
 def _build_net_map(doc: Document) -> dict[str, int]:
     """Assign integer net ids stable for this PCB. Net id 0 is reserved
     for "no net" (KiCad convention)."""
@@ -441,6 +515,53 @@ def write_pcb(
         ])
         stats.edge_cuts += 1
 
+    # Zones (POUR): copper pour outlines on signal layers. We emit just the
+    # boundary polygon and let KiCad's auto-filler do the actual copper
+    # generation — kicad-cli pcb drc fills before checking, so that's enough
+    # to resolve the GND/POWER pins that are routed through pour copper
+    # rather than discrete traces (the dominant source of "unconnected_items"
+    # before we exported zones).
+    zone_blocks: list = []
+    for oid, obj in doc.objects.items():
+        if obj.get("_type") != "POUR":
+            continue
+        kicad_layer = _kicad_layer(obj.get("layerId"), layer_map)
+        if not _is_copper(kicad_layer):
+            continue
+        outline = _decode_zone_path(obj.get("path"), origin_mm=board_origin_mm)
+        if len(outline) < 3:
+            stats.skipped += 1
+            continue
+        net_name = str(obj.get("netName") or "")
+        net_id = net_map.get(net_name, 0)
+        pts_block: list = [Sym("pts")] + [[Sym("xy"), x, y] for x, y in outline]
+        # `(filled_polygon)` echoes the boundary so kicad-cli treats the
+        # zone as already filled. Without this, kicad-cli pcb drc skips
+        # zones entirely (it never runs the auto-filler) and reports the
+        # entire GND/POWER net as unconnected. The user's POUR-drawn
+        # shape is also the truthful "intended copper area" — KiCad
+        # users can refill in the GUI to refine clearances/thermals.
+        filled_pts: list = [Sym("pts")] + [[Sym("xy"), x, y] for x, y in outline]
+        zone_blocks.append([
+            Sym("zone"),
+            [Sym("net"), net_id],
+            [Sym("net_name"), net_name],
+            [Sym("layer"), kicad_layer],
+            [Sym("uuid"), _new_uuid()],
+            [Sym("hatch"), Sym("edge"), 0.5],
+            [Sym("connect_pads"), [Sym("clearance"), 0.2]],
+            [Sym("min_thickness"), 0.2],
+            [Sym("filled_areas_thickness"), Sym("no")],
+            [Sym("fill"), Sym("yes"),
+                [Sym("thermal_gap"), 0.5],
+                [Sym("thermal_bridge_width"), 0.5]],
+            [Sym("polygon"), pts_block],
+            [Sym("filled_polygon"),
+                [Sym("layer"), kicad_layer],
+                filled_pts],
+        ])
+        stats.zones += 1
+
     # Vias
     for oid, obj in doc.objects.items():
         if obj.get("_type") != "VIA":
@@ -485,6 +606,7 @@ def write_pcb(
         *graphic_blocks,
         *track_blocks,
         *via_blocks,
+        *zone_blocks,
     ]
     write_pcb.last_stats = stats  # type: ignore[attr-defined]
     return to_sexpr(pcb, pretty=True)