docs: Audio workspace tab (Phase 1) — v1.3 changelog + README; drop orphaned transport spacer

main.py

@@ -4471,7 +4471,6 @@ class MainWindow(QMainWindow):
 
         # Extract audio area — an exact-length audio slice from the playhead,
         # saved via a Save As dialog (format follows the chosen extension).
-        transport_row.addSpacing(12)
         self._spn_audio_len = QDoubleSpinBox()
         # No practical upper cap — audio areas can be minutes long; ffmpeg stops
         # cleanly at end-of-file if the source is shorter. Arrows step by 1s;
@@ -4972,9 +4971,21 @@ class MainWindow(QMainWindow):
 
     # ── Changelog ────────────────────────────────────────────
 
-    APP_VERSION = "1.2"
+    APP_VERSION = "1.3"
     _SPLIT_HEADER_H = 22  # deck split-column header height (keep both deck spots in sync)
     CHANGELOG: list[tuple[str, list[str]]] = [
+        ("1.3", [
+            "<b>Audio workspace tab</b> — the <b>Scan</b> control-deck tab is "
+            "now <b>Audio</b>, a <code>QToolBox</code> with two panes. "
+            "<i>Extract &amp; Edit</i> has the audio-area length, an output "
+            "<b>format</b> picker (WAV / MP3 / FLAC / M4A / OGG / OPUS, "
+            "remembered), non-destructive <b>fade in/out, normalize, and "
+            "gain</b> applied on extract, a read-only <b>waveform</b> strip "
+            "(↻ to refresh), and <b>Play/Stop</b> audition of the current area "
+            "with the edits applied. <i>Scan / Classify</i> keeps the model, "
+            "threshold, and scan/auto/speech/review controls. The extract "
+            "length + button moved off the transport row into this tab.",
+        ]),
         ("1.2", [
             "<b>Per-tab export folder</b> — each file-list tab now remembers "
             "its own output folder; switching tabs follows that tab's folder. "