fix(capture): map deltacast audio from input 1; per-recorder channel/port; fix bridge stdin pipe

- Audio map: the deltacast bridge delivers audio on a separate FIFO wired as
  ffmpeg input 1, so the finalized master + HLS preview (and the growing
  orchestrator) now map audio via `audioMap` (1🅰️0? for deltacast, 0🅰️0? for
  DeckLink SDI / network) instead of an unconditional 0🅰️0?. Without this the
  deltacast master/preview carried no audio.
- Channel/port: spawn the bridge with --device = board index (default 0) and
  --port = source_config.port (falling back to the device index), so a recorder
  can capture from any of the board's 8 channels. Adds `port`/`board` params to
  start() and _buildInputArgs().
- Bridge stdin: the finalized-master ffmpeg reads the bridge's raw video from
  pipe:0, so its stdin must be 'pipe' when a bridge is present (was 'ignore',
  which made hiresProcess.stdin null and threw "Cannot read properties of null
  (reading 'on')" at bridgeProcess.stdout.pipe(...)).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

services/capture/src/capture-manager.js

@@ -559,7 +559,7 @@ class CaptureManager {
    * Returns { inputArgs, isNetwork }
    * @private
    */
-  async _buildInputArgs({ sourceType, sourceBackend = 'blackmagic', device, sourceUrl, listen, listenPort, streamKey }) {
+  async _buildInputArgs({ sourceType, sourceBackend = 'blackmagic', device, port, board, sourceUrl, listen, listenPort, streamKey }) {
     if (sourceType === 'srt') {
       let url;
       if (listen) {
@@ -599,9 +599,17 @@ class CaptureManager {
         throw new Error(`Failed to create audio FIFO ${audioFifo}: ${e.message}`);
       }
 
+      // ONE board (index 0) carries 8 channels (ports 0-7). --device is the
+      // board index, --port is the selected channel. board defaults to 0; the
+      // capture channel comes from source_config.port, falling back to the
+      // legacy device index so existing single-value recorders keep working.
+      const boardIdx = (typeof board === 'number' || /^\d+$/.test(String(board)))
+        ? parseInt(board, 10) : 0;
+      const portIdx  = (typeof port === 'number' || /^\d+$/.test(String(port)))
+        ? parseInt(port, 10) : idx;
       const bridge = spawn('deltacast-capture', [
-        '--device',           String(idx),
+        '--device',           String(boardIdx),
-        '--port',             String(idx),
+        '--port',             String(portIdx),
         '--audio-pipe',       audioFifo,
         '--signal-timeout',   '30',
       ], { stdio: ['ignore', 'pipe', 'pipe'] });
@@ -669,7 +677,7 @@ class CaptureManager {
    *
    * Returns the argv for spawn('bash', argv).
    */
-  _buildGrowingOrchestrator({ inputArgs, videoBitrate, resolution, framerate, audioChannels, outPath, hlsDir, videoCodec }) {
+  _buildGrowingOrchestrator({ inputArgs, videoBitrate, resolution, framerate, audioChannels, outPath, hlsDir, videoCodec, audioMap = '0:a:0?' }) {
     const { rawFlag, frameRate, ffRate } = deriveGrowingRaster(resolution, framerate);
     const vb = videoBitrate || GROWING_DEFAULT_BITRATE;
     const ach = audioChannels ? Number(audioChannels) : 2;
@@ -691,7 +699,7 @@ class CaptureManager {
       '-r', ffRate,
       '-f', 'mpeg2video', '@VF@',
       // (b) PCM s16le audio → "$AF"
-      '-map', '0:a:0?',
+      '-map', audioMap,
       '-c:a', 'pcm_s16le', '-ar', '48000', '-ac', String(ach),
       '-f', 's16le', '@AF@',
     ];
@@ -699,7 +707,7 @@ class CaptureManager {
     if (hlsDir) {
       ffHls = [
         // (c) H.264 HLS preview — GPU-gated, unchanged behaviour.
-        '-map', '[vlo]', '-map', '0:a:0?',
+        '-map', '[vlo]', '-map', audioMap,
         ...buildHlsVideoArgs(videoCodec, framerate),
         '-c:a', 'aac', '-b:a', '128k', '-ar', '44100',
         '-f', 'hls', '-hls_time', '2', '-hls_list_size', '15',
@@ -813,6 +821,10 @@ exit "$BMXRC"
     binId,
     clipName,
     device,
+    // Deltacast: one board (index 0) with 8 channels. `port` selects the
+    // channel; `board` selects the physical board (default 0).
+    port,
+    board,
     sourceType = 'sdi',
     // Source-backend selection for SDI capture (issue #168). Defaults to
     // `blackmagic` (DeckLink) so existing recorders are unaffected.
@@ -893,9 +905,14 @@ exit "$BMXRC"
 
     this._sessionIdForBridge = sessionId;
     const { inputArgs, isNetwork, bridgeProcess = null, audioFifo = null, interlaced = false } = await this._buildInputArgs({
-      sourceType, sourceBackend, device, sourceUrl, listen, listenPort, streamKey,
+      sourceType, sourceBackend, device, port, board, sourceUrl, listen, listenPort, streamKey,
     });
 
+    // Audio input index: the deltacast bridge delivers audio on a separate
+    // FIFO wired as ffmpeg input 1, whereas DeckLink SDI and network sources
+    // carry audio inside input 0. (bridgeProcess is set only for deltacast.)
+    const audioMap = bridgeProcess ? '1:a:0?' : '0:a:0?';
+
     // Non-growing master: ffmpeg muxes the finalized MOV directly. Growing
     // master: raw2bmx muxes the OP1a from elementary FIFOs (handled below via
     // the orchestrator), so we don't build ffmpeg codec args here for it.
@@ -935,7 +952,7 @@ exit "$BMXRC"
       catch (err) { console.error('[capture] could not create temp master dir:', err.message); }
     }
     const hiresOutput = localMasterPath;
-    const hiresStdio  = ['ignore', 'ignore', 'pipe'];
+    const hiresStdio  = [bridgeProcess ? 'pipe' : 'ignore', 'ignore', 'pipe'];
 
     // For SDI we cannot open the DeckLink device a second time for a preview
     // tee, so the live HLS preview is produced as a SECOND OUTPUT of the hires
@@ -967,6 +984,7 @@ exit "$BMXRC"
         outPath: growingPath,
         hlsDir: (sourceType === 'sdi') ? sdiHlsDir : null,
         videoCodec,
+        audioMap,
       });
       console.log('[capture] growing master via raw2bmx; orchestrator script length=' + orchArgs[1].length);
       hiresProcess = spawn('bash', orchArgs, { stdio: ['ignore', 'ignore', 'pipe'], detached: true });
@@ -978,14 +996,14 @@ exit "$BMXRC"
           ...inputArgs,
           '-filter_complex', '[0:v]yadif=mode=1:deint=1,split=2[vhi][vlo]',
           // Output 0 — ProRes/MOV master (local temp, uploaded to S3 on stop)
-          '-map', '[vhi]', '-map', '0:a:0?',
+          '-map', '[vhi]', '-map', audioMap,
           ...hiresCodecArgs,
           hiresOutput,
           // Output 1 — low-latency H.264 HLS preview for the UI monitor.
           // GPU-encoded (h264_nvenc) when the GPU is attached to this sidecar,
           // otherwise libx264 (issue #164). GOP is pinned to one IDR per HLS
           // segment so segments start on keyframes (avoids black/flashing).
-          '-map', '[vlo]', '-map', '0:a:0?',
+          '-map', '[vlo]', '-map', audioMap,
           ...buildHlsVideoArgs(videoCodec, framerate),
           '-c:a', 'aac', '-b:a', '128k', '-ar', '44100',
           '-f', 'hls', '-hls_time', '2', '-hls_list_size', '15',