Phase 1: import .vstpreset in offline render (loadSerializedState)

daw_vst_bridge --render now applies a VST3 preset when job has 'preset'
(base64 of a .vstpreset file). Parse the SDK binary chunk format with
PresetFile (vst3sdk), rewrap component/controller state into the bridge
blob [4B BE compLen][comp][4B BE ctrlLen][ctrl] and apply via
loadSerializedState before rendering. SF2/SFZ ignore preset (warning).
Bad base64/magic/chunks fail the job with rc 1 and no partial clip.

Tests: golden Nexus .vstpreset fixture; VST3 with/without preset,
bad preset -> rc 1, non-VST3 preset ignored. 20/20 pass.

native_bridge/include/RenderJob.h

@@ -12,6 +12,9 @@
 //             bpm?, soundfont_bank?, soundfont_program?,
 //             notes: [{pitch?, velocity?, start_beat?, duration_beats?}] }
 //   instrument_type: 0=VST3, 1=VST2, 2=SF2/SF3, 3=SFZ (InstrumentType enum).
+//   preset: base64 of a .vstpreset file (VST3 only; SF2/SFZ ignore it). The
+//           bridge parses the SDK chunk format and applies component/controller
+//           state via loadSerializedState before rendering.
 //   pitch/velocity: velocity 0..1 (float) or 0..127; start/duration in beats.
 //
 // Returns 0 on success. On failure prints a clear error to stderr and returns