Import Keebio-Parts.pretty (MIT, keebio/Keebio-Parts.pretty)

Vendor footprint library for mechanical-keyboard hardware (switches,
stabilizers, encoders, connectors, MCU/passive footprints), added
whole as MIKILAB_Keebio_Parts under footprints/mechanical, following
the same "keep vendor .pretty intact" precedent as altera.pretty /
xilinx.pretty / lattice.pretty.

Rewrote every 3D model reference that leaked the original author's
absolute local paths (/Users/danny/..., /Library/Application
Support/kicad/...) so the library stays self-contained:
- resolvable refs -> ${KIPRJMOD}/3dmodels/mechanical/Keebio-Parts/...
  (7 STEP files actually present upstream, copied alongside)
- genuinely missing vendor assets -> ${KISBLIB}/Keebio-Parts.pretty/...,
  the same known-gap convention already used for other vendor
  libraries in this repo
- one hardcoded stock-KiCad path -> ${KISYS3DMOD}/...
Also stripped a stray "Sheet file" property pointing at the original
author's own project.

fp-lib-table/.global regenerated from the tree; MANIFEST.csv rows
added for every imported footprint and 3D model. check_library.py:
0 errors (was 0 before, still 0).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TnzoFuRZAhRGeHAdz8UzR2

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