Add compact synth introspection queries

[linuxificator]

Small transport-neutral introspection layer for embedded AMY.

Design constraints:

• no per-patch UI metadata, labels, ranges, units, or administrative control lists in AMY
• reuses AMY's existing live synth readback (yield_synth_commands)
• works uniformly for built-in patches, memory patches, and directly configured synths such as Karplus-Strong
• returns complete technical wire state; clients may derive/filter user-facing controls on the host side
• no heap allocation in the query path

Protocol namespace:

• ?iv -> introspection protocol version
• ?is<N> -> replayable wire-state lines for synth N, terminated by !ie

amy-message exposes the same queries as a reference transport. A dedicated C regression test covers namespace/version, direct KS state, built-in patch state, undefined synths, and malformed requests.