Phase 21 Direction B: bound network memory via Range-segmented forward fetch

Replace the open-ended forward GET with sequential bounded bytes=start-end
segments, the next fetched only when the scheduler drains below low-water,
so the browser holds ~one segment regardless of file size. Seek converges
on the same loop. Strip BP-DIAG.

DeepDrftPublic/Interop/audio/PlaybackScheduler.ts

@@ -107,14 +107,6 @@ export class PlaybackScheduler {
     // Mutated by evaluateProductionPause() — named to signal the state-advance on each call.
     private productionPaused_: boolean = false;
 
-    // ─────────────────────────────────────────────────────────────────────────────────────────
-    // [BP-DIAG] Phase 21.4 back-pressure diagnostic. TEMPORARY — strip once the cause is confirmed
-    // in Daniel's browser run. Throttles evaluateProductionPause() logging to one line per ~250 ms
-    // so the console shows the live lookahead / byte-estimate / latch without flooding (the signal
-    // is evaluated on every chunk + every poll). Grep "[BP-DIAG]" in the browser console.
-    private bpDiagLastLogMs: number = 0;
-    // ─────────────────────────────────────────────────────────────────────────────────────────
-
     // Callbacks
     public onPlaybackEnded: (() => void) | null = null;
 
@@ -245,22 +237,6 @@ export class PlaybackScheduler {
             this.productionPaused_ = true;
         }
 
-        // [BP-DIAG] Phase 21.4 — the single source of truth for the latch decision. If `paused`
-        // never goes true while bytes keep arriving, the lookahead is not growing as expected:
-        // inspect `lookahead` vs `high` (should cross 30 during a fast fill) and `bufCount`/`bytes`
-        // (decode must actually be populating the scheduler). Throttled to ~4 Hz. TEMPORARY — strip
-        // once the cause is confirmed. (Uses performance.now when present; Date.now fallback.)
-        const bpNow = (typeof performance !== 'undefined' ? performance.now() : Date.now());
-        if (bpNow - this.bpDiagLastLogMs >= 250) {
-            this.bpDiagLastLogMs = bpNow;
-            console.log(
-                `[BP-DIAG] evaluateProductionPause paused=${this.productionPaused_} ` +
-                `lookahead=${lookahead.toFixed(2)}s high=${this.forwardHighWaterSeconds} low=${this.forwardLowWaterSeconds} ` +
-                `bytes=${(this.getDecodedByteEstimate() / (1024 * 1024)).toFixed(1)}MB cap=${(this.maxDecodedBytes / (1024 * 1024)).toFixed(0)}MB ` +
-                `overByteCeiling=${overByteCeiling} bufCount=${this.buffers.length} pos=${this.getCurrentPosition().toFixed(2)}s ` +
-                `decodedEnd=${(this.getTotalDuration() + this.playbackOffset).toFixed(2)}s active=${this.isActive_}`);
-        }
-
         return this.productionPaused_;
     }