Unified entry point: automatically detects LAS/LAZ/COPC format and parses points.

Format Detection

• LAS: LASF magic, version ≤ 1.3, no compression bit
• LAZ: LASF magic, any version, compression bit set at byte 104 (requires laz-support feature)
• COPC: LASF magic, version 1.4, compression bit set, COPC VLR present (requires laz-support feature)

All three formats use the same decompression path internally. COPC adds spatial indexing but falls back to full decompression for the auto path.