docs(planning): generate codebase map via gsd-map-codebase

.planning/codebase/STRUCTURE.md

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+# STRUCTURE
+
+## Root Directory (`/`)
+- `youtube_tab_to_pdf.py`: The massive core application runner (1k+ lines). Handles downloading, cv2 matrix manipulation, OCR, stitching, and PDF rendering.
+- `video_cv_tracker.py`: Extracted Temporal/Motion tracker logic responsible for analyzing page flips based on median column mutations instead of simplistic frame diffs.
+- `sim_stitch.py` / `simulate_ocr_pipeline.py`: Legacy or simulation variations used to mock or prototype OCR/stitching behaviors without redownloading heavy videos.
+- `test_pipeline.py` / `diag_v2.py`: Pipeline integration testers and diagnostic tools for manual CV metric validation.
+- `bootstrap.bat` / `bootstrap.sh`: Lifecycle and setup scripts for CI or new user initialization.
+
+## `/scripts`
+- Contains focused debugging scripts (`debug/test_full_ocr.py`, `debug/rigorous_validator.py`) utilized to isolate OCR misfires or to rigidly assert measure numbers.
+
+## `/docs`
+- `devlog/`: Contains markdown logs of development insights (e.g., `2026-03-29_postmortem_duplicate_row_bug.md`).
+
+## `/.planning`
+- Contains project requirements, roadmaps, and this codebase mapping.