Extension rail icons — v4 current set

v4 = the flat set with Julius's round-3 picks folded in: Custom Mockups negative gear (gear punched out of the solid tee — no halo at all) and Pexels official tile with the P enlarged 1.3× (the verbatim mark's P is too small at rail size). For the record: Gemini Flash had voted tight halo on the gear; Julius overrode. All earlier rounds preserved below and via footer permalinks.