Add the interface, then rebuild the economy around the first playtest

The MVP is playable: a turn screen, a career retrospective, an optional
feedback widget, local-storage autosave with file export/import, and a build
that flattens everything into one self-contained HTML file.

A turn has two phases — the scenario and its options, then what the choice did
and, separately, what the day cost regardless. Numbers that move without the
player seeing why are most of what makes them meaningless. Locked options are
shown greyed with the requirement spelled out rather than hidden, so a player
can see the door they cannot open yet.

The interface is named entirely by the pack. `pack.display` maps a state path to
a label, a format and an order, which is why the header reads "Standing" for a
path called `reputation` and why debt disappears while it is zero.

The first playtest then found three things, all of them fair.

*"Wasn't clear what daily drain was for."* The ledger was labelling changes by
the path that moved — "Money −$18" — when the upkeep entry that caused them had
a perfectly good name. It now says "Coffee, transit, lunch". The labels were in
the data the whole time and never reached the screen.

*"Should probably pay rent weekly / get paid every other week… would be good to
have day of week and week # shown."* Packs can now declare a calendar, and the
engine derives the day name, cycle and index from the turn number before the
event is drawn — so content can require a Friday and the header can say
"Thursday · Week 2 · Day 12". Upkeep entries take `every` and `offset`, making
wages fall on alternate Fridays and rent every Monday. The turn screen carries
a diary line — "Wages tomorrow · Rent in 4 days" — computed generically from
whatever a pack schedules.

*"Always in debt — could never get ahead."* The old economy bled $25 a day
regardless of play. It is now roughly break-even at baseline, with a
`spare_shift` event that appears *because* you are broke: the way out of a hole
should be visible from inside it. Across archetypes a careful player ends around
$1,400, an unplanned one treads water, and a careless one sinks into real debt.

That retune broke the coverage test, usefully. Random play stopped reaching hard
times at all, which made the entire debt branch look dead — it was not, since
random play is not a plausible player. Coverage is now the union across five
archetypes, including one that is broke *and* well-liked, because the "ask a
friend for money" options sit in a state no single-axis strategy reaches.

Not covered by any of this: styling and dark mode, which only a human with a
browser can check. This machine has none that can render a page.

109 tests. Reasoning in docs/DECISIONS.md §14-21.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VMSFHyVPitUoosW5wyEADj

src/ui/format.js

@@ -0,0 +1,151 @@
+// Turning state paths and conditions into English.
+//
+// Display names, number formats and which stats appear in the header all come
+// from the pack's `display` map, so a new setting renames and re-orders the
+// interface without touching the UI. Anything the pack does not describe falls
+// back to a derivation from the path itself, so content is never *required* to
+// supply a label just to be playable.
+
+import { getPath } from '../engine/paths.js';
+import { check } from '../engine/conditions.js';
+
+const titleCase = (text) =>
+  text.replace(/_/g, ' ').replace(/^\w/, (c) => c.toUpperCase());
+
+/** The pack's display rules for a path, if it has any. */
+export function displayFor(pack, path) {
+  return pack.display?.[path] ?? null;
+}
+
+/** A human name for a path, derived from the path when the pack is silent. */
+export function labelFor(pack, path) {
+  const declared = displayFor(pack, path)?.label;
+  if (declared) return declared;
+
+  const segments = path.split('.');
+  if (segments[0] === 'relationships' && segments.length === 3) {
+    const character = pack.characters?.find((c) => c.id === segments[1]);
+    const stat = pack.relationshipStats?.[segments[2]]?.label ?? titleCase(segments[2]);
+    return `${character?.name ?? titleCase(segments[1])} — ${stat.toLowerCase()}`;
+  }
+  return titleCase(segments.at(-1));
+}
+
+/** Money is written as money; everything else is a plain number. */
+export function formatValue(pack, path, value) {
+  if (typeof value === 'boolean') return value ? 'yes' : 'no';
+  if (displayFor(pack, path)?.format === 'money') return formatMoney(value);
+  return String(value);
+}
+
+export function formatMoney(amount) {
+  const rounded = Math.round(amount);
+  const body = `$${Math.abs(rounded).toLocaleString('en-US')}`;
+  return rounded < 0 ? `−${body}` : body;
+}
+
+/** A signed change, for the outcome list: "+$45", "−3". */
+export function formatDelta(pack, path, from, to) {
+  const delta = to - from;
+  if (displayFor(pack, path)?.format === 'money') {
+    return `${delta > 0 ? '+' : '−'}$${Math.abs(Math.round(delta)).toLocaleString('en-US')}`;
+  }
+  return `${delta > 0 ? '+' : '−'}${Math.abs(delta)}`;
+}
+
+/**
+ * One condition as a requirement the player can read: "Negotiation 15+",
+ * "Trevor — likes you 48+", "not in debt".
+ */
+export function describeCondition(pack, condition) {
+  if (!condition || typeof condition !== 'object') return '';
+  if (Array.isArray(condition)) return condition.map((c) => describeCondition(pack, c)).join(', ');
+  if (condition.all) return condition.all.map((c) => describeCondition(pack, c)).join(', ');
+  if (condition.any) return condition.any.map((c) => describeCondition(pack, c)).join(' or ');
+  if (condition.not) return `not ${describeCondition(pack, condition.not)}`;
+
+  const { path, op, value } = condition;
+  const label = labelFor(pack, path);
+
+  if (typeof value === 'boolean') return value ? label.toLowerCase() : `no ${label.toLowerCase()}`;
+
+  const amount = formatValue(pack, path, value);
+  switch (op) {
+    case '>=': return `${label} ${amount}+`;
+    case '>': return `${label} over ${amount}`;
+    case '<=': return `${label} ${amount} or less`;
+    case '<': return `${label} under ${amount}`;
+    case '==': return `${label} exactly ${amount}`;
+    case '!=': return `${label} other than ${amount}`;
+    default: return `${label} ${op} ${amount}`;
+  }
+}
+
+/** What a locked option is waiting for. */
+export function requirementText(pack, failedConditions) {
+  const parts = failedConditions.map((c) => describeCondition(pack, c)).filter(Boolean);
+  return parts.length ? `Needs ${parts.join(', ')}` : 'Not available yet';
+}
+
+/**
+ * The stats the header shows, in the pack's declared order, skipping anything
+ * the pack marks hidden or asks to hide while it is zero.
+ */
+export function headerStats(pack, state, schema) {
+  return Object.entries(pack.display ?? {})
+    .filter(([, rule]) => !rule.hidden)
+    .map(([path, rule]) => ({
+      path,
+      rule,
+      label: labelFor(pack, path),
+      value: getPath(state, path),
+      bounds: schema[path],
+    }))
+    .filter((stat) => !(stat.rule.hideWhenZero && !stat.value))
+    .sort((a, b) => (a.rule.order ?? 99) - (b.rule.order ?? 99));
+}
+
+/**
+ * How the current turn is titled. A pack with a calendar gets its day name and
+ * cycle ("Thursday", "Week 2 · Day 12"); one without falls back to the turn
+ * number alone, which is what the engine guarantees.
+ */
+export function turnHeading(pack, state) {
+  const unit = capitalize(pack.turnUnit ?? 'turn');
+  const name = state.calendar?.name;
+  if (!name) return { title: `${unit} ${state.turn}`, detail: null };
+
+  const cycleName = pack.calendar?.cycleName ?? 'Cycle';
+  return {
+    title: name,
+    detail: `${cycleName} ${state.calendar.cycle} · ${unit} ${state.turn}`,
+  };
+}
+
+/**
+ * The pack's scheduled upkeep, as "what is coming and when". Answers the
+ * question a player actually has — when am I next paid, when is rent due —
+ * without them having to reverse-engineer it from the ledger.
+ */
+export function upcomingUpkeep(pack, state, { limit = 3 } = {}) {
+  const upcoming = [];
+  for (const entry of pack.upkeep ?? []) {
+    if (!entry.every || !entry.label) continue;
+    if (!check(state, entry.requires).passed) continue;
+
+    const offset = entry.offset ?? 0;
+    const elapsed = state.turn - 1 - offset;
+    const turnsAway = elapsed < 0 ? -elapsed : (entry.every - (elapsed % entry.every)) % entry.every;
+    const amount = (entry.effects ?? [])
+      .filter((e) => e.op === 'add' && typeof e.value === 'number')
+      .reduce((sum, e) => sum + e.value, 0);
+
+    upcoming.push({ label: entry.label, turnsAway, incoming: amount > 0 });
+  }
+  return upcoming
+    .sort((a, b) => a.turnsAway - b.turnsAway)
+    .filter((entry, index, all) => all.findIndex((e) => e.label === entry.label) === index)
+    .slice(0, limit);
+}
+
+const capitalize = (text) => text.charAt(0).toUpperCase() + text.slice(1);