port: withdraw the dual-mono generalisation -- the measurement stands, the rule does not

I argued `highest_rate` had no case because ADV's higher-rate presentation is
dual-mono while its louder one is mono-in-stereo, so the extra bytes buy a
duplicated channel rather than fidelity. The Decoder tested that disc-wide over
the 28 three-stream cues: the stream-3/stream-2 size ratio runs min 0.0778,
median 1.2565, max 2.9163, sd 0.5057, with only 12 of 28 within 15% of 1.0, and
declared rates scatter with them. A 37x spread is not a duplicated channel.

The CHANNEL MEASUREMENT STANDS -- ADV chunk 1 is mono-in-stereo and chunk 2 is
dual-mono at -8.318574, this port's own decode, which the Decoder could not
re-run and did not dispute. What fails is the step from one asset to the format.

NOTHING IN THE EXPORT CHANGES. `loudest` is a per-asset content rule -- it reads
the peak of the streams in front of it -- so a scattering structural ratio cannot
undermine it. What changes is the REASON, in four places: authored/audio.json's
presentation_why, the selector comment in audio.rs, BLOCKED.md's row, and
DECISIONS.md. The honest statement is narrower: `highest_rate` was never refuted,
it was never argued for, and neither is `loudest`. That is why the entry is
marked CHOSEN rather than measured, and why one capture deletes it.

Recorded on the pattern rather than just the instance: this is the third claim of
mine in two iterations that generalised a single-asset observation, after "the
chunks are two stems" and "everything the sequencer paces off rest.t is late".
All three were true of the thing I looked at. The failure is reaching for the
rule a measurement would imply if it held everywhere and writing that down in the
same breath as the measurement.

Also noted, not mine and not affecting export_voice: S12B's three streams are
byte-size identical, and BIRD_224 is three-stream while not being a movie cue.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N7FiFFFwbvG2uxdcEh8HyF

authored/audio.json

@@ -135,19 +135,26 @@
    "different streams: ADV chunk 1 is 1118268 B at 0.0 dBFS, chunk 2 is",
    "1171516 B at -8.3 dBFS.",
    "",
-   "The reason for switching is a measurement of this port's, not a preference.",
-   "The case for `highest_rate` was that more bytes per second means a better",
-   "encode. It does not, here: ADV chunk 1 is MONO-IN-STEREO (channel 2",
-   "digitally silent) and chunk 2 is DUAL-MONO (both channels identical at",
-   "-8.318574). So chunk 2's extra bytes go into encoding a duplicate of its own",
-   "channel, not into fidelity, and the byte-rate difference is explained without",
-   "any appeal to quality. That removes the only argument for it.",
+   "WHY `loudest` AND NOT `highest_rate`: this is a PER-ASSET CONTENT choice,",
+   "and that is the whole of its justification. The disc masters its other audio",
+   "near full scale -- the SE cues decode to +0.18 dBFS -- and S00A's only",
+   "surviving full-length stream is its louder one at -4.2 dBFS, so `loudest`",
+   "makes the two cutscenes' dialogue sit at comparable levels instead of 4.4 dB",
+   "apart. Neither half is strong alone; together they are what there is.",
    "",
-   "What is left points the other way, and both parts are weak on their own:",
-   "the disc masters its other audio near full scale (the SE cues decode to",
-   "+0.18 dBFS), and S00A's only surviving full-length stream is its louder one",
-   "at -4.2 dBFS -- so `loudest` makes the two cutscenes' dialogue sit at",
-   "comparable levels instead of 4.4 dB apart.",
+   "⚠️ A STRUCTURAL ARGUMENT WAS OFFERED HERE AND IS WITHDRAWN. It said ADV",
+   "chunk 1 is mono-in-stereo (channel 2 digitally silent) while chunk 2 is",
+   "dual-mono (channels identical at -8.318574), therefore the extra bytes",
+   "encode a duplicated channel rather than fidelity, therefore the rate",
+   "argument collapses. The CHANNEL MEASUREMENT stands -- it is ADV's, and it is",
+   "this port's own. THE GENERALISATION DOES NOT. The Decoder tested it",
+   "disc-wide over the 28 three-stream cues: the stream-3/stream-2 size ratio",
+   "runs min 0.0778, median 1.2565, max 2.9163, sd 0.5057, with only 12 of 28",
+   "within 15% of 1.0, and declared rates scatter with them (S06A: 5661 against",
+   "16513 B/s). A 37x spread is not a duplicated channel.",
+   "",
+   "So `highest_rate` was not refuted as a rule; it was simply never argued for,",
+   "and neither was this. That is why the entry is CHOSEN and why it says so.",
    "",
    "STILL A CHOICE. One capture of the intro with dialogue audible settles it,",
    "and it is the last unforced decision in the voice pipeline."