port: apply the measured positional weights, keyed by byte size

ADV's three chunks map onto the Decoder's contexts exactly, each a declared
byte_size plus the 60-byte RIFF header. authored/audio.json gains
voice.stream_weights keyed by SIZE, and the exporter weights only when every kept
stream matches, falling back to the divisor otherwise.

The key is the check: two weeks ago these same sizes did not fit the region the
resolver returned, which is how the 238-packet late start was found. Applied
positionally the weights would have gone onto the wrong streams silently. S00A
matches nothing and keeps the divisor. ADV mixes at 0.4142/0.2929/0.2929, -2.87.

Unlooked-for confirmation: the filter folds chunks 0 and 2 from two live channels
and chunk 1 from one, found independently by live_channels, matching their claim
that ctx1 is the only stream with a silent channel.

Also files an UNEXPLAINED regression: verify-menu-audio's dead-press check now
reports DIFFER across three runs, diverging at 0.085 s with different durations.
Not diagnosed, not the voice change, and left failing rather than silenced. The
check's premise is cross-run bit-determinism, which is what made it strong and
also what makes it brittle.

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

authored/audio.json

@@ -200,6 +200,46 @@
    "clean audible dialogue, so nothing in the output reveals that two streams",
    "are missing. That is why the manifest says it in words on every voice entry",
    "rather than leaving it to this file."
-  ]
+  ],
+  "stream_weights": {
+   "_": [
+    "Declared XMA `byte_size` -> the coefficient that stream's position takes in a",
+    "stereo downmix. MEASURED by the RE agent 2026-08-30",
+    "(docs/re/structures/intro-audio-decomposed.md): decomposing the game's own",
+    "6-channel output as capture = 0.600 x movie + residual puts ctx0 at FL/FR,",
+    "ctx1 at FC with LFE silent, and ctx2 at BL/BR.",
+    "",
+    "🔴 KEYED BY BYTE SIZE ON PURPOSE. The assignment is indexed by the decoder's",
+    "own declared size, so the exporter can CHECK that the stream in front of it is",
+    "the one the measurement describes rather than assume it. A region whose chunks",
+    "do not match falls back to the count divisor and says so. That is not defensive",
+    "programming: on 2026-08-30 this table's sizes did NOT fit the region the",
+    "resolver returned, which is what exposed `resolve_movie_voice_region` starting",
+    "238 packets late. Had the weights been applied positionally they would have",
+    "been applied to the wrong streams silently.",
+    "",
+    "⚠️ ONE BOOT, ONE MOVIE. Only `ADV`'s three streams were measured. `S00A`'s",
+    "sizes match nothing here and it keeps the divisor -- extending this by",
+    "POSITION would be assuming the ordering generalises, which is exactly the",
+    "inference the byte-size key exists to avoid.",
+    "",
+    "⚠️ The weights are a stereo downmix's, folded to mono. They sum to 1.0, so the",
+    "total is the movie's own; what they distribute is the balance between three",
+    "positions. Whether the game's 0.600 mixer gain is a constant or a volume",
+    "setting is unknown and the port applies no gain of its own."
+   ],
+   "1294336": {
+    "position": "FL/FR",
+    "weight": 0.4142
+   },
+   "1118208": {
+    "position": "FC (LFE silent)",
+    "weight": 0.2929
+   },
+   "1171456": {
+    "position": "BL/BR",
+    "weight": 0.2929
+   }
+  }
  }
 }