opal-rust v3.0.0-1

Changed

• Binds opal 3.0.0. The emulation core is new. The eight C functions keep
  their names and C signatures. Rendered output is not bit-identical to 2.0.2.
• Opal is now a wrapper around the raw mirror, which moved to
  opal::ffi::Opal. It derefs to it, so reads such as chip.op[3].eg_out
  compile unchanged. Field writes and struct literals no longer compile. The C
  core trusts fields such as algorithm, multiple, f_number,
  queue_head, and sample_rate, so a bad value written from safe code was
  undefined behavior, in 2.0.2-2 as well. The unsafe methods
  Opal::raw_mut and Opal::from_raw give write access. Their safety
  sections list the fields that must stay in range. The opal::ffi
  functions now take *mut ffi::Opal instead of *mut Opal, so a call that
  passed &raw mut chip passes chip.raw_mut() instead.
• Struct mirrors follow the new layout. The visualizer fields keep their names
  and meaning. Those are envelope_stage, eg_out, key, mod_source, and
  out on Operator, and op_slot, pair_index, out_source, chan_type,
  left_pan, and right_pan on Channel. The core no longer reads
  mod_source, out_source, or chan_type, so writing them no longer
  changes the sound. Other fields may be renamed, retyped, or rescaled.
• WriteBuf is now QueuedWrite, with fields due, reg_num, and value.
  output_enable replaces the old per-speaker flags. Opal::opl3_enabled is
  now new_mode. sample_counter replaces chip_timer. tremolo_depth and
  vibrato_depth hold the BDh bits that tremolo_shift and vib_shift
  encoded as shifts. hi_hat_phase and cymbal_phase hold the phases that
  the rm_* bits sampled. The write-buffer cursors are queue, queue_head,
  queue_count, chip_samples, and last_due. Fields that used to be bool
  are u8, matching uint8_t in the header.
• Operator and channel register fields hold raw register values.
  sustain_level keeps its name but is now a u8 from 0 to 15 instead of a
  scaled u16 level. Reads that don't name its type still compile and get
  different numbers. total_level, multiple, feedback, f_number, and
  block replace output_level, freq_mult_times2, feedback_shift,
  freq, and octave. algorithm replaces alg and uses a new encoding.
  The envelope rates and waveform are u8 too.
• NEW (register 105h bit 0) still gates new writes. While it is clear, bank 1
  writes other than 105h land in bank 0, E0h writes keep only waveforms 0-3,
  and a C0h write turns on both speakers. Changing NEW no longer rewrites
  stored state or how it plays, so a waveform 4-7 written while NEW was set
  keeps playing after NEW is cleared. All 18 channels keep playing, and
  four-operator pairs follow register 104h alone.
• A masked timer sets nothing. Setting a timer's mask bit clears a flag that
  is already set. IRQ stays set only while a flag is set.
• Opal::new and set_sample_rate treat a rate of 0 as 49716 Hz. Anything
  above i32::MAX - 49716 clamps to that limit. A u32 that does not fit in
  a C int is passed as c_int::MAX, which the core then clamps.
  set_sample_rate no longer clears the write queue or the output history, so
  a queued write survives it. It still resets the resampler phase in
  sample_accum. pan clamps a level above 127.
• Opal::new still leaves every operator in release with eg_out at 0x1FF.
  It now enables both speakers on every channel, so a voice is audible without
  a C0 write. The instance is about 66 KiB.

Added

• Tests for the 3.0.0 behavior. NEW leaves stored state alone. Bank 1 writes
  reach bank 1, and waveforms 4-7 are stored, only while NEW is set.
  Four-operator pairing stays after NEW is cleared. Masked timers set nothing. Sample-rate clamping, the
  write queue surviving set_sample_rate, and pan clamping are covered too.
  So is a raw copy wrapped back with from_raw, and a compile_fail doctest
  checks that safe code cannot write chip state.
• Notes on the update are in doc/3.0.0.md.

Removed

• Operator::slot_index, Operator::chan_index, and Channel::chan_index.
  op_slot, modulator_slot, and carrier_slot map channels to operators.
• Internal state that upstream dropped, including phase_out, phase_reset,
  eg_ksl, fb_mod, cha, chb, chc, chd, vib_pos, the eg_*
  envelope timer fields, and rhythm_reg.