PWR_FLAG instances use a #FLG reference prefix, not #PWR, so their
pin positions were never registered as virtual connection anchors in
_parse_virtual_connections. As a result, find_orphaned_wires reported
wire ends terminating on a PWR_FLAG as dangling. Other call sites
(schematic_analysis.py:127, kicad_interface.py:3814) already recognize
#FLG as a power symbol; align this site with them.
Also coerce a previously-validated Optional[int] to int in board/layers.py
so the file passes mypy (required by the pre-commit hook); behavior is
unchanged because the value is already None-checked above.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>