feat(v0.4.0): vNext — closed-loop world model + settlement contract

Implements the vNext architecture from the research doc: demote the noisy
multi-rail planner in favour of a closed loop (world truth → invariant check)
plus a single utility-driven goal authority.

L1 services (fix no_drop / silent pathfinder hang first):
- InventoryLedger: diff-based "did I actually get it" verifier; acquire-food
  now confirms via ledger.gainedSince instead of the unreliable count/event.
- MotionService.gotoSafe: wall-clock timeout + progress watchdog +
  path_update(noPath/timeout) → structured {reached|stuck|timeout|nopath}.

L3 plan — unify the three competing rails (curriculum/manifesto/storyline):
- Settlement Contract: ordered M0–M9 milestones, each invariant-checked
  against an authoritative world view (early steps delegate to the proven
  curriculum; late game adds farming).
- InvariantChecker + predicate library; GoalManager selects the lowest unmet
  milestone via utility argmax (food-urgency preempts, DEPS-style).
- Wired into the scheduler: bot.js precomputes snapshot.contract; reflex.js
  consumes it in place of the storyline rail. Manifesto L0 still preempts.

Eval + robustness:
- Village Score (single 0..1 metric) on the snapshot + TUI "build" line.
- survive.dig-in skill + dusk_dig_in mode (exposed at night, no bed → cover).
- approach_block helper (GoalNear + lookAt, avoids GoalLookAtBlock #341).

+28 new tests (450 total green). LLM remains entirely off the tick path.

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

runtime/modes.js

@@ -138,3 +138,28 @@ registerMode({
 		return { action: { skillId: "survive.sleep" }, detail: { reason: "night with bed in hand" } };
 	},
 });
+
+// QW8 — displaced at night with no bed: dig in for cover instead of standing
+// in the open getting shot. Fires only when night_shelter can't (no bed) and
+// no hostile is already in melee (self_preservation owns that). Requires a
+// placeable cap block; survive.dig-in's preconditions enforce dig safety.
+registerMode({
+	name: "dusk_dig_in",
+	description: "Night, no bed, exposed → dig a hole and cap it",
+	interrupts: ["curriculum"],
+	update(ctx) {
+		const snap = ctx?.snapshot;
+		if (!snap || snap.isDay !== false) return null; // only on explicit night
+		if (ctx.modeCooldown?.dusk_dig_in && Date.now() < ctx.modeCooldown.dusk_dig_in) return null;
+		const inv = snap.inventory || {};
+		if (Object.keys(inv).some((n) => /_bed$/.test(n))) return null; // night_shelter handles beds
+		// Only when actually exposed at night and away from a known shelter.
+		const sheltered = !!snap.locations?.shelter || snap.hazards?.headBlock && snap.hazards.headBlock !== "air";
+		if (sheltered) return null;
+		const hasCap = Object.keys(inv).some((n) => /(_planks|_log|cobble|stone|dirt|sand|gravel|netherrack)$/i.test(n));
+		if (!hasCap) return null;
+		ctx.modeCooldown = ctx.modeCooldown ?? {};
+		ctx.modeCooldown.dusk_dig_in = Date.now() + 60_000;
+		return { action: { skillId: "survive.dig-in" }, detail: { reason: "exposed at night, no bed" } };
+	},
+});