Public-ready: JSON tune specs, first-class loop API, licence, AGENTS.md

- MidiFile.set_loop(): one call writes LOOP_START/END, RPR LOOP
  START/END (Reaper) and LoopBegin/End markers - every engine finds
  its dialect; reader now parses markers and the smoke test asserts
  the round-trip
- tools/make_tune.py: declarative JSON spec -> fully arranged MIDI
  with style presets (dos_adventure, n64_ambient, chiptune_racing);
  the agent-friendly front door, no Python required
- tunes/specs/: demo tune 04 'Tea Break at the Terminal' (Am/112,
  loop bars 4-20) generated entirely from JSON
- AGENTS.md: spec schema, score grammar, verification loop, looping
  conventions for game BGM
- MIT LICENSE; history audited clean of credentials

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 Kevin Hermes (an AI agent) and Steve Calcott
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.