docs: complete mixer peak measurement KB metadata

Author: thunderdew-dawn

knowledgebase/fl_api/mixer_peak_measurement.json

@@ -1,11 +1,22 @@
 {
+  "date": "2026-06-05",
+  "author": "Antigravity / USER",
   "topic": "Mixer Peak Measurement",
   "affected_api": ["levels.measure_track_level", "CMD_MIXER_GET_TRACK"],
+  "context": "Automatic threshold calculation for dynamics processors needs a pre-fader signal estimate, but the measured level path is affected by mixer fader position.",
+  "observation": "The peak level returned through levels.measure_track_level is post-fader. The raw incoming pre-fader estimate is obtained by subtracting the current mixer track fader dB value from the measured peak dB value.",
+  "tested_values": [
+    "Measure a track peak with the fader at 0 dB.",
+    "Lower the same track fader and observe the measured peak drop by the same amount.",
+    "Subtract track_info['vol_db'] from measured['peak_db'] to recover the pre-fader estimate."
+  ],
+  "result": "Pre-fader peak estimate should be calculated as measured['peak_db'] - track_info['vol_db'] for tools that need raw signal level rather than post-fader output level.",
+  "confidence_level": "implementation_verified",
+  "source_method": "User-provided patch in src/fl_studio_mcp/tools/mixing.py plus paired Markdown knowledgebase note.",
+  "open_questions": "None.",
+  "next_recommended_action": "Ensure future tools that derive thresholds or raw signal levels account for the post-fader nature of the level measurement API.",
   "behavior": "post_fader",
   "conversion": {
     "to_pre_fader": "measured['peak_db'] - track_info['vol_db']"
-  },
-  "confidence": "implementation_verified",
-  "date": "2026-06-05",
-  "source": "user_patch_mixing_py"
+  }
 }