organ: the rest of the peripheral moves into El

The speaker and the voice-fetch landed in the previous commit. This is the
remainder of the 939-line Swift program, ported, and the line it draws is
between DEVICE and ARITHMETIC rather than between languages.

Two things stay realizers, because they are the two things El cannot express
as arithmetic: handing a buffer to the DAC and waiting for it to drain
(el_audio_darwin.m), and asking the OS for samples off a mic or frames off a
camera (el_capture_darwin.m). Both are their own translation units declared
in el_runtime.h, never patches to el_runtime.c.

Everything else is El. WAV decode, LPC autocorrelation, Levinson-Durbin at
order 16, formant extraction off the all-pole envelope, source-filter
resynthesis, and the three descriptors are organ_dsp.el. Consent, disclosure
and the scene descriptor are organ.el. Barge-in, yield-or-hold, backchannel
and resume are organ_converse.el.

The organ never learns a word. Codes and phoneme geometry arrive from the
language side; the organ turns them into samples and gets the samples out the
speaker, and runs the same trip in reverse for the senses. No lexicon, no
grapheme-to-phoneme, by design.

Barge-in needed pause/resume and a real DAC position rather than a tick
counter, because "finish the buffer" is not barge-in and a queue holding
three buffers is a third of a second wrong about where it is. An injected
barge also had to fire once rather than stay true, which is otherwise a
livelock the moment a backchannel resumes.

Measured against the Swift on out/mic_room.wav: seconds, rms, peak, zcr,
centroid and F0 agree to every printed digit; formants F1-F5 and bandwidths
B1-B5 are identical. imitate cannot match bit-for-bit because the Swift
excites unvoiced frames with Double.random — two Swift runs correlate 0.957
with each other and El correlates 0.958 with Swift, so the port is as close
to the original as the original is to itself.

Verified end to end: consent fails closed on both locks, real mic capture
(16000 frames), real camera frame (1920x1080 -> 15 numbers), voiceprint,
imitate, hear-imitate, a voice learned by ear and fetched back out of the
engram, and all five converse paths with real audio. The binary contains
zero afplay/Swift strings and spawns no child process while speaking.

lang/runtime/el_runtime.h

@@ -126,10 +126,18 @@ el_val_t  speaker_play_wav(el_val_t path);         /* 16-bit mono RIFF/WAVE; 1 o
  * the hardware is still going; speaker_played_frames() is how far it actually
  * got, which is what makes an interrupted utterance resumable at the sample. */
 el_val_t  speaker_play_pcm16_async(el_val_t samples, el_val_t sample_rate);
+el_val_t  speaker_play_wav_async(el_val_t path);
+el_val_t  speaker_pause(void);     /* stop AT THIS SAMPLE, keep position */
+el_val_t  speaker_resume(void);    /* carry on from exactly there */
 el_val_t  speaker_playing(void);
 el_val_t  speaker_stop(void);
 el_val_t  speaker_played_frames(void);
 
+/* WAV geometry without playing — wav-info, and the segment duration converse
+ * needs to turn elapsed time into progress. */
+el_val_t  wav_frames(el_val_t path);
+el_val_t  wav_rate(el_val_t path);
+
 /* Microphone (afferent). Fails CLOSED: returns 0 unless the OS has granted
  * capture access. mic_capture_pcm16 blocks for `seconds` and returns an [Int]
  * of 16-bit mono samples at `sample_rate` — the raw stream is handed to El and