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Two strands of in-progress work, committed together because they overlap in sras_workers.py and main_window.py. Min peak frequency floor: - CACH tail bumped to version 4, adding u32 min_freq_khz provenance in fixed-point kHz (a float32 20.1 reads back as 20.10000038 and would report a spurious mismatch forever). v1-v3 tails read as no floor. - Stored FFT caches are accepted when the reader's floor is at or above the stored one, since a higher floor is re-applicable by masking. - Floor plumbed through compute_rf_image, BatchCacheWorker and the viewer. Batch Export View as Images: - New sras_render.py holds draw_view_image, shared by the Qt canvas and the headless exporter so a PNG cannot drift from what the GUI shows. Deliberately Qt-free so it is importable in a pool subprocess. - BatchExportImagesWorker renders the current view settings across many files, process-pooled with an inline fallback, reporting per-file output names so the caller can flag same-stem collisions. - _axes_extent extracted into sras_format for both render paths. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>