v1.13.0

Additive (MINOR) release: an engine-agnostic rig model so a feedpak can carry tone information
natively — a structured, portable alternative to the opaque tones.definitions passthrough.

Added

• New optional side-file rigs.json (§7.9) and manifest rigs
  key: a pack-level library of rigs, each an ordered set of effect blocks. Every block splits
  what it is (intent, engine-independent) from how to render it (realizations — an ordered
  preference list over nam / ir / plugin / builtin engines, extensible to future ones). Open
  role/kind/engine vocabularies, an open normalized params map with optional time
  automation, and an optional graph for non-serial topology (parallel amps, wet/dry, stereo).
  schemas/rigs.schema.json.
• Arrangement tones (§6.9) gains base_rig and
  changes[].rig, referencing a rig id in rigs.json. The legacy opaque tones.definitions
  passthrough is unchanged; a rig-aware Reader prefers the structured references.
• examples/extended.feedpak now ships a rigs.json and a tones block that exercises it.

Compatibility

• Purely additive. Older Readers ignore the rigs key, rigs.json, and the new base_rig/rig
  fields, and still load. Nothing is removed, renamed, or repurposed.