test: cover mid-read cancellation

[snkmcb]

Summary

• add GeoTIFF window cancellation coverage after the first segment boundary
• verify the partial RasterGrid is released and no later segment is read
• mark memory-budget enforcement and tile-boundary cancellation as implemented

Validation

• source diagnostics report no errors
• git diff --check passes
• focused CMake build was attempted but the configured MSVC environment could not resolve the standard header cstdint