opal-zig v1.0.2-1

Added

• First release, binding opal 1.0.2.
• The opal module compiles the upstream C11 core from the pinned release tarball with
  the Zig build system. No code generation step, no dependency beyond libc.
• Opal, Channel, Operator, and WriteBuf mirrored as extern struct with
  snake_case field names. The test suite verifies every struct size and field offset
  against the C compiler, so layout drift fails loudly.
• Methods wrapping the eight C functions (init, setSampleRate, port,
  portBuffered, flushWriteBuf, pan, sample, read), plus create and
  destroy to heap-pin an instance under the C core's no-copy rule, and render to
  fill interleaved stereo buffers.
• modulatorSlot and carrierSlot helpers matching the channel-to-slot table
  documented in the upstream header.
• A demo (zig build run) that renders a short FM arpeggio to opal-demo.wav.