sehnsucht v0.2.1

Bug-fix release, no new features.

Fixed

• HSC playback follows HSC-Tracker HSCOBJ 1.4 / HSCPLAY. Unmatched effects
  including 0x3n, 0x5n, 0x6n, and 0xDn set speed. 0x08 is 0x40.
  Notes use the original 16-bit frequency word. 0x1n/0x2n slide the low
  byte by n + 1. 0xAn/0xBn/0xCn replace the level byte without keeping
  KSL. An instrument-set with slide 0 leaves the key off. A repeat
  instrument-set of the current patch is a no-op. Out-of-range order indexes
  play empty rows instead of looping. The 51st order slot is played. The KSL
  xor applies to the carrier always, and to the modulator only in additive
  mode. Checked against all 234 modules in playlists/hsc.m3u.
• HSC tracker cells show effect & 0x7F for an instrument-set and the
  unclamped octave n / 12, matching playback.
• RAD v2 note-retrigger uses each channel's last instrument at play time
  (Reality CChannel.LastInstrument), not a load-time latch shared across
  channels and reset per pattern. A note without an instrument change no
  longer forces a key-on bounce. An instrument byte still updates the latch
  when the patch is missing or the row is a tone slide.
• CMF General-MIDI channel-9 drum remap loads AdPlug's five fallback
  percussion patches onto rhythm channels 11..15, instead of file
  instrument 0. The fallbacks live in a side table, so they cannot collide
  with file patch numbers.
• AudioT archives with Wolf-engine extensions .vsi (Blake Stone: Planet
  Strike), .co7 (Corridor 7), and .bc (Operation Body Count) default to
  the 700 Hz IMF timer, not Keen's 560 Hz.

Changed

• Format guides for HSC, RAD, CMF, and AudioT describe HSCOBJ playback,
  Reality last-instrument retrigger, GM drum fallbacks, and Wolf-engine
  AudioT rates.