feat(v0.4.0): finish vNext plan — anti-loop, skill-graph, worldDelta diff, flee→motion

Completes the remaining v0.4.0 plan items and one fix motivated by a live
in-game observation (flee hanging 30s against a persistent zombie).

- flee → MotionService.gotoSafe: structured {stuck|timeout|nopath} in ~4s with
  a blind-retreat fallback, instead of the observed 30s pathfinder hang + 3
  watchdog replans. Movements setup guarded so it is unit-testable.
- QW5 anti-loop (runtime/anti-loop.js): same skill failing >=3x in 5min →
  30min blacklist (reflex shouldSkip) + one-shot improvement_request
  (bot.js drainFired -> writeProposal).
- 4.1 closed-loop worldDelta: runSkill snapshots inventory before execute and
  attaches the real delta (_invObserved) to every successful result; opt-in
  skill.expectGain asserts the claimed gain or returns world_unchanged.
- 3.6 skill-graph (Plan4MC): declarative requires/produces for ~20 skills;
  prerequisitesMet/canRun/runnableFrontier; GoalManager annotates suggestions
  with blockedBy when prereqs are unmet.

+22 tests (472 total green). Live smoke confirmed dig-in works and no new
errors; flee loop is what this commit's flee migration addresses.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

runtime/skills/flee.test.js

@@ -0,0 +1,62 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+
+import { skill } from "./flee.js";
+
+function vec(x, y, z) {
+	return {
+		x, y, z,
+		clone() { return vec(x, y, z); },
+		distanceTo(o) { return Math.hypot(x - o.x, y - o.y, z - o.z); },
+		offset(dx, dy, dz) { return vec(x + dx, y + dy, z + dz); },
+	};
+}
+
+function fakeBot({ moveOnForward = 0 } = {}) {
+	const bot = {
+		entity: { position: vec(0, 64, 0), yaw: 0 },
+		entities: { z1: { name: "zombie", position: vec(2, 64, 0) } },
+		loadPlugin() {},
+		pathfinder: { goto: () => new Promise(() => {}), stop() {}, setMovements() {} },
+		setControlState(name, on) {
+			if (name === "forward" && on && moveOnForward) {
+				bot.entity.position = vec(moveOnForward, 64, 0);
+			}
+		},
+		async look() {},
+	};
+	return bot;
+}
+
+test("flee returns done when motion reaches the retreat point", async () => {
+	const bot = fakeBot();
+	const ctx = { bot, motion: { gotoSafe: async () => ({ ok: true, code: "reached", movedBlocks: 16 }) } };
+	const res = await skill.execute(ctx, {});
+	assert.equal(res.ok, true);
+	assert.equal(res.code, "done");
+	assert.ok(res.worldDelta.fledTo);
+});
+
+test("flee falls back to blind retreat and succeeds when it moves far enough", async () => {
+	const bot = fakeBot({ moveOnForward: 8 });
+	const ctx = { bot, motion: { gotoSafe: async () => ({ ok: false, code: "stuck", movedBlocks: 0 }) } };
+	const res = await skill.execute(ctx, { blindMs: 20 });
+	assert.equal(res.ok, true);
+	assert.equal(res.detail.mode, "blind-retreat");
+});
+
+test("flee surfaces the structured motion code when stuck and blind retreat fails", async () => {
+	const bot = fakeBot({ moveOnForward: 0 }); // never moves
+	const ctx = { bot, motion: { gotoSafe: async () => ({ ok: false, code: "stuck", movedBlocks: 0 }) } };
+	const res = await skill.execute(ctx, { blindMs: 20 });
+	assert.equal(res.ok, false);
+	assert.equal(res.code, "stuck");
+});
+
+test("flee precondition fails with no hostile", () => {
+	const bot = fakeBot();
+	bot.entities = {};
+	const pre = skill.preconditions({ bot }, {});
+	assert.equal(pre.ok, false);
+	assert.equal(pre.code, "no_hostile");
+});