src/oscillators: Any PCM with at least 512 samples can be a wavetable.

[dpwe]

Loosens the conditions on what can be treated as a wavetable, following request of @ernesto on Discord.

The code assumes each cycle in the wavetable file is exactly 256 samples. However, the PCM file can contain any number of them, as long as it has at least 2 (so there are at least two wave shapes to interpolate).

On playback, the phase value interpolates within the table, dividing the range between 0.0 and 1.0 into as many interpolation intervals as there are distinct waveforms in the wavetable (minus 1).

To play an arbitrary sound as a wavetable:

>>> amy.load_sample('../Downloads/trim_bit.wav', preset=32)
Loaded sample over wire protocol. Preset #32. 11844 bytes, 5922 frames, midinote 60
>>> amy.send(synth=1, num_voices=4, oscs_per_voice=1)
>>> # eg0 controls amplitude envelope, eg1 controls phase i.e. waveform from the wavetable.
>>> amy.send(synth=1, osc=0, wave=amy.WAVETABLE, preset=32, duty='0.0,0,0,0,1.0', 
             eg0='20,1,9960,1,20,0,20,0', eg1='0,0,10000,1,100,1')

[bwhitman]

⛓️ tulipcc integration PR opened

This merge was pinned into tulipcc for full-system CI: shorepine/tulipcc#1254

Test it there and merge that PR to move tulipcc onto this AMY.

[github-actions]

🎛️ AMY HW CI (AMYboard bench)

Flashed this PR's AMY (LoadTestChord: 6-voice Juno patch=1, one held note every 2 s) onto the physical AMYboard and measured the smoothed render load as the chord grows — back-to-back with the same sketch built at the PR's merge base, so Δ is this PR's own cost.

✅ PASS — the bench ran the test to completion.

notes held	main @ 1170461	this PR	Δ
1	1018	1015	-3
2	1179	1180	+1
3	1744	1746	+2
4	1926	1927	+1
5	2564	2560	-4
6	2743	2744	+1

Full chord settled render μs: 2740 (was 2741, Δ -0.0%) (peak 2748, 39 samples)

⬇️ Artifacts: serial log · load trace · report

_{Self-hosted bench (amyboardci). FAIL means only that the test could not run — the load values are informational, with no threshold and no audio compare. See tools/arduino_loadsweep/.}