Make RustRaptor the repository root and track its playable bundle

mods/iron_coast_boss_6/README.md

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+# Iron Crown boss
+
+A standalone API 1 mod for the Iron Coast finale. It adds a new command
+Dreadnought with broad armored wings and three forward cannon pods, matching
+the industrial overhead style of the original game. The package has no mod
+dependencies and does not replace any original or Iron Coast enemy definition.
+
+- Enemy: `iron_coast_boss_6:unit`; health 160, reward 1800, air boss, logical 96×64.
+- Weapon: `iron_coast_boss_6:projectile`; damage 3, speed 4, logical 8×8.
+- Objective: every actual boss death increments `iron_coast_boss_6:defeated`.
+- Entry: fly downward to y 24, then patrol between x 80 and x 144.
+- Attack: every 54 simulation ticks, alternate a three-shell fan with two
+  straight cannon lanes. A rising charging sound begins nine ticks before
+  each volley. At 70/3 Hz this gives 0.386 seconds warning before a 2.314-second
+  volley cycle. Charging creates no explosion effects.
+- State: per-entity patrol direction, age and volley cursor; removed on death.
+  Supports the finale's two staged bosses and simultaneous spawns. It never
+  completes a mission directly or fires from retired entities.
+
+Difficulty uses the engine's original boss health rule: definitions retain 160
+health, and the two lower difficulty levels spawn bosses with 80 health.
+
+`art/unit-sd.png` and `art/unit-hd.png` share one centered 96×64 logical canvas.
+The HD texture is 768×512 (8×) and the SD version is derived from the same
+transparent generated master. The cannon shell likewise has matching 8×8 and
+64×64 versions. `art-qa.json` records bounds and source hashes. The supplied
+alpha is preserved; runtime colors with alpha below 128 remain transparent.
+
+The built-in imagegen tool generated both masters. Exact prompts live in
+`prompts/`; `provenance.json` records their outputs. All authored images and
+sounds belong in Git. Original sprite references remain outside this package.
+
+Reproduce the deterministic sounds and SD/HD reductions with:
+
+```sh
+python3 RustRaptor/mods/iron_coast_boss_6/build_assets.py
+```
+
+`--audio-only` needs only Python's standard library. `audio-recipe.json`
+records seeds, PCM properties and hashes. The sounds are non-silent PCM16
+mono 22050 Hz charging, firing and destruction cues; no recordings are used.
+
+Validate activation and lifecycle behavior using the production simulation:
+
+```sh
+CARGO_TARGET_DIR=RustRaptor/target cargo run --offline \
+  --manifest-path RustRaptor/mods/iron_coast_boss_6/validation/Cargo.toml
+```
+
+The validation checks alternating patterns, warning timing, independent
+entity state, serialized state restoration, death counter/reward behavior,
+dead-enemy firing guards and two staged encounters on all four difficulties.
+`validation-results.json` records the controlled outcomes. The complete
+mission 6 mod runs separate campaign and balance checks with its other enemies.