March 18: Gain Normalization and the Crab Nebula Pipeline

The composite pipeline gained per-tile gain normalization to eliminate exposure-level grid artifacts, quality scoring via HTTP response headers, and HDR auto-stretch for extreme dynamic range targets like the Crab Nebula. Coverage-aware filter selection in the recipe engine now handles RA wraparound correctly.

What shipped

PR	Title
#872	fix: coverage-aware filter selection in recipe engine
#870	feat: per-tile gain normalization to eliminate exposure-level grid artifacts
#867	feat: composite quality scoring, streaming reprojection, HDR auto-stretch, input file sorting