[screen] boredom: the sky forgets, the ledger does not

No shipments for a sustained stretch and the corruption eases back toward clean.
The LEDGER is untouched -- history is not erased, only the display decays -- so
resuming production puts the targets straight back and the picture walks home in
about a second.

60s grace then 180s decay: a jam you notice, diagnose and fix costs nothing.
The player has to genuinely walk away before the sky starts cleaning itself.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

fktry/src/screen/boredom.test.ts

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+import { describe, expect, it } from 'vitest';
+import { BOREDOM_GRACE_SECONDS, BOREDOM_HORIZON_SECONDS, freshness } from './boredom';
+
+describe('boredom decays the display, slowly', () => {
+  it('shows everything you earned while production is running', () => {
+    expect(freshness(0)).toBe(1);
+    expect(freshness(5)).toBe(1);
+  });
+
+  it('does not punish a normal jam', () => {
+    // The whole grace window plus a beat: a stall long enough to notice, diagnose and fix
+    // must leave THE SCREEN exactly as the player left it.
+    expect(freshness(BOREDOM_GRACE_SECONDS)).toBe(1);
+    expect(freshness(BOREDOM_GRACE_SECONDS - 1)).toBe(1);
+  });
+
+  it('takes minutes, not seconds, to forget', () => {
+    // A minute of silence has barely dented it; the sky is patient.
+    expect(freshness(BOREDOM_GRACE_SECONDS + 30)).toBeGreaterThan(0.8);
+    // Fully clean only after the player has genuinely walked away.
+    expect(BOREDOM_GRACE_SECONDS + BOREDOM_HORIZON_SECONDS).toBeGreaterThanOrEqual(180);
+  });
+
+  it('reaches clean at the horizon and stays there', () => {
+    expect(freshness(BOREDOM_GRACE_SECONDS + BOREDOM_HORIZON_SECONDS)).toBe(0);
+    expect(freshness(BOREDOM_GRACE_SECONDS + BOREDOM_HORIZON_SECONDS + 9999)).toBe(0);
+  });
+
+  it('decays monotonically', () => {
+    let prev = 2;
+    for (let s = 0; s <= BOREDOM_GRACE_SECONDS + BOREDOM_HORIZON_SECONDS + 60; s += 5) {
+      const f = freshness(s);
+      expect(f).toBeLessThanOrEqual(prev);
+      expect(f).toBeGreaterThanOrEqual(0);
+      prev = f;
+    }
+  });
+
+  it('sits at half way through the decay', () => {
+    expect(freshness(BOREDOM_GRACE_SECONDS + BOREDOM_HORIZON_SECONDS / 2)).toBeCloseTo(0.5, 5);
+  });
+
+  it('treats a nonsense idle time as fresh rather than wiping the sky', () => {
+    expect(freshness(NaN)).toBe(1);
+    expect(freshness(-10)).toBe(1);
+  });
+});

fktry/src/screen/boredom.ts

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+/**
+ * Boredom — the factory's work evaporating off THE SCREEN.
+ *
+ * If nothing ships for a long stretch, the sky slowly forgets. The corruption LEDGER is
+ * untouched: history is not erased, only the display decays. So when production resumes the
+ * targets are instantly back where they were and the picture snaps home in about a second.
+ *
+ * The horizon is deliberately generous. A jam, a rebuild, a rethink of the bus — none of
+ * those are supposed to read as punishment. The player should have to genuinely walk away
+ * before the sky starts cleaning itself.
+ */
+
+/** No shipments for this long before the sky begins to forget at all. */
+export const BOREDOM_GRACE_SECONDS = 60;
+/** ...and this long again to fade from full corruption to clean. */
+export const BOREDOM_HORIZON_SECONDS = 180;
+
+const clamp01 = (x: number) => Math.min(1, Math.max(0, x));
+
+/**
+ * How much of the ledger's corruption is still on display, 0..1.
+ * 1 = everything you earned is showing; 0 = the sky has forgotten (the tallies have not).
+ */
+export function freshness(idleSeconds: number): number {
+  if (!(idleSeconds > BOREDOM_GRACE_SECONDS)) return 1; // NaN-safe: unknown idle reads as fresh
+  return 1 - clamp01((idleSeconds - BOREDOM_GRACE_SECONDS) / BOREDOM_HORIZON_SECONDS);
+}