Format imported KiCad symbol and footprint files in pcb search

[akhilles]

Note

Medium Risk
Moderate risk because it changes how downloaded KiCad assets are parsed/rewritten and written back to disk, which could affect compatibility with edge-case vendor symbol/footprint files.

Overview
pcb search now formats imported/generated KiCad S-expression files (.kicad_sym, .kicad_mod) via the new pcb-sexpr formatter, including formatting footprints after STEP embedding.

It also rewrites the symbol property "Footprint" value to the local lib:footprint form derived from the downloaded footprint path, then generates the .zen file from the exact formatted symbol content; adds a unit test for the footprint-property rewrite and wires in the pcb-sexpr dependency.

^{Written by Cursor Bugbot for commit 3c07b45. This will update automatically on new commits. Configure here.}