fix(task-14): per-space resolution, mirrored inserts, tags above the box, per-axis scale

Closes the four verified BLOCKING findings on pid_graph.

1. scope="all" attached across layouts: the port grid, bbox candidates,
   vertex grid, junctions and text lookup were pooled from every space.
   The grid is now keyed by (space, cell) and every lookup filters by the
   edge's space; junctions carry `space`.
2. A mirrored INSERT (extrusion -Z, as MIRROR3D / foreign DXFs store it)
   got its catalogue ports on the unmirrored image at 1.0. Both engines
   report `mirrored` on INSERT properties (ezdxf: extrusion z < 0; COM:
   Normal z < 0; default False); transform_port takes `mirrored` and
   applies x -> -x about the WCS insertion point after rotation/scale,
   direction (180 - d) mod 360 — cross-checked against Insert.matrix44.
   resolve_endpoint passes it through too, so draw_line starts on the
   mirror image as well.
3. The text-tag fallback searched a full circle around the box top, so a
   line label or note below the symbol beat the tag above it. Candidates
   must now sit at or above top - height/2 (spec §9.2 step 6), nearest
   wins, and line-number texts are never equipment tags.
4. A non-uniform INSERT scale re-ran the transform with the X factor and
   set `inferred` (reserved for foreign-block ports). transform_port
   gains `strict=False` for the reader: point ports scale per axis
   exactly; a radial port keeps min(sx, sy)·r and the node drops to 0.6
   with notes ["non-uniform scale"]. Node dicts gain `y_scale`,
   `mirrored` and `notes` (default []).

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd

backends/ezdxf_backend.py

@@ -845,6 +845,11 @@ def _entity_info_dxf(ent) -> EntityInfo:
             props["x_scale"] = ent.dxf.xscale if ent.dxf.hasattr("xscale") else 1.0
             props["y_scale"] = ent.dxf.yscale if ent.dxf.hasattr("yscale") else 1.0
             props["rotation_deg"] = ent.dxf.get("rotation", 0.0)
+            # MIRROR3D and foreign DXFs store a mirror as extrusion -Z (the
+            # stored x unnegated); `insertion` above is already WCS, but the
+            # block's content is drawn on the mirror image about it, so a
+            # reader that places catalogue ports needs to know.
+            props["mirrored"] = float(extrusion[2]) < 0
             # The drawn symbol alone. ``bounding_box`` below takes the ATTRIBs
             # with it, so a TAG above a valve pushes the box past the body and
             # a line ending on the body's real edge reads as *inside* it.