Validate POC A and POC B foundations

CONTRIBUTING.md

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+# Contributing to Ransom's Wake
+
+## Definition of ready
+
+Before implementation, a change must identify:
+
+- the player-visible outcome;
+- the owning production layer;
+- the authoritative source of state;
+- the behavior that will prove completion;
+- any save, input, accessibility or performance consequence.
+
+If ownership is unclear, resolve it before writing code. If a change introduces
+a new dependency direction or global service, write an ADR first.
+
+## Definition of done
+
+A change is complete only when:
+
+- no second implementation of the same rule exists;
+- public boundaries use explicit typed data;
+- unit tests cover new domain behavior;
+- integration tests cover changed scene or service wiring;
+- every corrected bug has a regression test, or a documented reason why not;
+- error and empty states are handled;
+- relevant documentation and baselines are updated;
+- `bash scripts/quality_gate.sh` passes from the repository root.
+
+Visual behavior additionally requires a check at 1280 × 720 and at the smallest
+supported in-game presentation size. Human readability cannot be inferred from
+mesh counts or screenshots alone, so playtest observations remain evidence.
+
+## Change discipline
+
+- Keep one conceptual change per commit.
+- Prefer deletion or extraction over parallel implementations.
+- Do not rename and redesign unrelated systems in the same change.
+- Never modify generated `.godot/` content.
+- Keep assets separate from gameplay state and reference them through resources.
+- Treat warnings, leaked nodes and nondeterministic tests as defects to triage,
+  even if the process returns exit code zero.
+
+## Review checklist
+
+- Is there exactly one owner for each new rule?
+- Does dependency flow match `docs/ENGINEERING_GUARDRAILS.md`?
+- Can the domain behavior run without a scene tree?
+- Can UI code only observe or issue commands?
+- Are time, randomness and external I/O controllable in tests?
+- Is failure behavior tested?
+- Is a prototype implementation being copied instead of translated?
+- Would a future save migration be required?
+- Does the quality gate pass?