Fix Memory-management issues from TODO.md

- JaySynth's destructor now uses delete[] to match every new T[n]
  allocation (m_pVoices, pPer_voice_controls, pCurrNoteInfos,
  humanize_voice_param[i], ppHumanizedSliders[i], m_ppAudioThread,
  m_ppEventAudioThreadRdy), fixing undefined behavior from the
  mismatched scalar delete.
- Found and fixed the same new[]/delete mismatch pattern via
  ScopedPointer in PluginProcessor.cpp: ScopedPointer always calls
  scalar delete (per JUCE's own doc comment "do not give it an array
  to hold!"), so ScopedPointer<char> holding a new char[...] in
  setStateInformation/setCurrentProgramStateInformation had the same
  bug. Replaced both with HeapBlock<char>, JUCE's array-owning,
  malloc/free-backed smart pointer.
- Added a shared SynthCheckAlloc() helper (synth_defs.h/synth_debug.c)
  that aborts with a diagnostic instead of returning NULL, and wrapped
  all 24 malloc call sites across the C DSP core (env.c, lfo.c, vcf.c,
  vco.c, blit.c, wavetable.c, voice.c, param_scale.c). All are
  one-time init/bufsize-change calls, never in the per-block render
  path, so this adds no real-time-thread overhead.

Verified with clean debug and release builds (no new warnings/errors)
and a full link.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011dhtwRLARk4eiPngcQykLJ

src/synth/vco.c

@@ -87,7 +87,7 @@ void VCO_SetBufsize(osc_t *pObj, UINT32 size)
 	if (!size)
 		return;
 
-	pObj->pOut = (synth_float_t*)malloc(pObj->bufsize*sizeof(synth_float_t));
+	pObj->pOut = (synth_float_t*)SynthCheckAlloc(malloc(pObj->bufsize*sizeof(synth_float_t)));
 
 }