firmware(mini): fix native DEMO playback + boot-hold race; bridge: PLAY grammar + query passthrough

DEMO rig-static root cause: the dedicated prio-6 PlaybackTask on core 1 entered
its loop once and was never scheduled again (instrumented: 'TASK up' printed,
then zero heartbeats and idx frozen at 0 while prio-7 CueTask on the same core
ran fine). Playback now runs INLINE in CueTask (playbackStep): single clock,
fractional accumulator paces the file rate against cueLoopHz, ZOH into the
shared target. Verified on hardware: idx advances, telemetry varies, loop works.

Boot home-hold race: a SOURCE:/PLAY: command arriving during the 3s hold was
clobbered by the boot-source apply; runtime choice now wins.

Bridge: play 'loop' sends firmware grammar PLAY:LOOP=1 + PLAY:START (bare
PLAY:LOOP was 'unknown'); allowlist adds PLAY:STATUS and SOURCE? queries.

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

Author: knaufinator

bridge/control_api.py

@@ -328,11 +328,15 @@ def _set_source(self, source: Optional[str]) -> dict:
         return {"source": self.source, "motion_gated": self.source != SOURCE_LIVE}
 
     def _play(self, action: Optional[str]) -> dict:
-        mapping = {"start": "PLAY:START", "stop": "PLAY:STOP", "loop": "PLAY:LOOP"}
-        cmd = mapping.get(action)
-        if cmd is None:
+        # Firmware grammar (main.cpp): PLAY:LOOP=1 enables looping (bare
+        # PLAY:LOOP is 'unknown'); loop = enable looping AND start playing.
+        mapping = {"start": ["PLAY:START"], "stop": ["PLAY:STOP"],
+                   "loop": ["PLAY:LOOP=1", "PLAY:START"]}
+        cmds = mapping.get(action)
+        if cmds is None:
             raise _ApiError(f"bad_play_action:{action}")
-        self._serial.send_cmd(cmd)
+        for c in cmds:
+            self._serial.send_cmd(c)
         self.play_state = {"start": "playing", "stop": "stopped",
                            "loop": "looping"}[action]
         self._broadcast(self._status_event())
@@ -344,7 +348,7 @@ def _play(self, action: Optional[str]) -> dict:
     # (those have dedicated, state-tracked verbs) or arbitrary strings.
     _CMD_ALLOW = ("MCA:", "MCA?", "SERVO:", "TELRATE:", "TELRATE?",
                   "CONFIG:", "CONFIG?", "BITS:", "BITS?", "SCALE?", "VERSION?",
-                  "FINGERPRINT?")
+                  "FINGERPRINT?", "PLAY:STATUS", "SOURCE?")
 
     def _cmd(self, text: Optional[str]) -> dict:
         if not text or not isinstance(text, str):

mini/main/main.cpp

@@ -590,30 +590,36 @@ static inline void decodeSeqFrame(const uint8_t* p, float raw[6]) {
 // PlaybackTask is now a PRODUCER: it paces to the file rate and pushes each
 // sample into the shared target (raw M6P2 -> TGT_RAW so CueTask cues it;
 // baked M6P1 -> TGT_BAKED). CueTask does the IK/servo at cueLoopHz.
-static void PlaybackTask(void* pv) {
-    (void)pv;
-    uint16_t rate = (seqRateHz ? seqRateHz : 50);
-    TickType_t period = pdMS_TO_TICKS(1000 / rate);
-    if (period < 1) period = 1;
-    TickType_t last = xTaskGetTickCount();
-    for (;;) {
-        if (playbackActive && seqSamples && seqCount) {
-            float raw[6];
-            decodeSeqFrame(seqSamples + (size_t)playbackIdx * seqStride, raw);
-            writeTarget(raw, g_framesRaw ? TGT_RAW : TGT_BAKED);
-            uint32_t nxt = playbackIdx + 1;
-            if (nxt >= seqCount) {
-                if (playbackLoop) {
-                    nxt = seqLoopPoint;
-                } else {
-                    playbackActive = false;
-                    nxt = 0;
-                    serial_printf("PLAY:DONE\r\n");
-                }
+// Playback producer, run INLINE from CueTask each cue tick (no separate task:
+// a dedicated prio-6 PlaybackTask on core 1 was observed entering its loop and
+// then never being scheduled again on this build — folding the producer into
+// the one task that demonstrably runs also gives a single clock, no cross-task
+// handoff). Paces the sequence at seqRateHz via a fractional accumulator and
+// pushes the current frame into the shared target as ZOH.
+static void playbackStep(uint16_t cueRateHz) {
+    static float acc = 0.0f;
+    if (!(playbackActive && seqSamples && seqCount)) { acc = 0.0f; return; }
+
+    float raw[6];
+    decodeSeqFrame(seqSamples + (size_t)playbackIdx * seqStride, raw);
+    writeTarget(raw, g_framesRaw ? TGT_RAW : TGT_BAKED);
+
+    // Advance at the file rate regardless of the cue loop rate.
+    acc += (float)(seqRateHz ? seqRateHz : 50) / (float)(cueRateHz ? cueRateHz : 50);
+    while (acc >= 1.0f) {
+        acc -= 1.0f;
+        uint32_t nxt = playbackIdx + 1;
+        if (nxt >= seqCount) {
+            if (playbackLoop) {
+                nxt = seqLoopPoint;
+            } else {
+                playbackActive = false;
+                nxt = 0;
+                serial_printf("PLAY:DONE\r\n");
+                break;
             }
-            playbackIdx = nxt;
         }
-        vTaskDelayUntil(&last, period);
+        playbackIdx = nxt;
     }
 }
 
@@ -639,6 +645,10 @@ static void CueTask(void* pv) {
         }
         const float dt = 1.0f / (float)curRate;
 
+        // DEMO producer: feed the shared target from the embedded sequence
+        // (inline; see playbackStep comment). No-op unless playbackActive.
+        playbackStep(curRate);
+
         float ch[6]; int64_t ts; int fmt;
         readTarget(ch, &ts, &fmt);
         int64_t age = esp_timer_get_time() - ts;
@@ -1305,7 +1315,7 @@ extern "C" void app_main(void) {
         serial_printf("PLAY: sequence ready -- %u samples @ %uHz, %d-bit, %s, loop@%u (~%.1fs)\r\n",
             (unsigned)seqCount, (unsigned)seqRateHz, seqBits, g_framesRaw ? "raw" : "baked",
             (unsigned)seqLoopPoint, (double)seqCount / (seqRateHz ? seqRateHz : 50));
-        xTaskCreatePinnedToCore(PlaybackTask, "Playback", 4096, NULL, 6, NULL, 1);
+        // Playback runs inline in CueTask (playbackStep) — no separate task.
     } else {
         serial_printf("PLAY: no valid embedded sequence\r\n");
     }
@@ -1323,8 +1333,13 @@ extern "C" void app_main(void) {
 #endif
 
     // ── Apply the boot source (OFF / DEMO / LIVE), default = DEMO ─────
+    // Skip if a runtime SOURCE:/PLAY: command already changed the source
+    // during the hold (don't clobber an operator's explicit choice).
     Source bootSrc = loadBootSource();
-    if (bootSrc == SRC_DEMO && !haveSeq) {
+    if (g_source != SRC_OFF) {
+        serial_printf("SOURCE: runtime source=%s set during hold - boot default skipped\r\n",
+                      sourceName(g_source));
+    } else if (bootSrc == SRC_DEMO && !haveSeq) {
         serial_printf("SOURCE: boot=DEMO but no sequence -> OFF\r\n");
         setSource(SRC_OFF);
     } else {