feat(custom): model reader-authored games and events

The data layer for PRD F13, with no UI and no behaviour change yet.

src/shared/custom.ts defines the two key spaces, their schemas, and the
projection into what the views read. Two properties are the point of it:

- A reader's event id is random, not derived from their title. They can type a
  scraped event's exact name and date, which under ${game}:${slug}:${date} is a
  byte-identical key — one completion mark and one streak silently shared by two
  events. Randomness also means renaming their own event never moves its id.
- A reader's event carries no sourceUrl, so a hand-entered date can never be
  attributed to a source, and claims no region split, because they entered one
  instant and inventing three would fabricate two of them.

The rest is widening what was GameId-shaped into a lane that may be one of
theirs: clockFor takes the boundary fields structurally so their events run on
the identical countdown rather than a second one, day keys fall back to the
regional default for a lane with no server map, and gameMeta becomes a context
resolver so metaFor stays pure and total — a lane can outlive its game when an
import carries an event whose game did not come with it.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

src/shared/games.ts

@@ -1,3 +1,4 @@
+import type { CustomGames, LaneId } from "./custom.ts";
 import type { GameId, Region } from "./schema.ts";
 
 export interface GameMeta {
@@ -72,3 +73,48 @@ export const GAME_LIST: GameMeta[] = Object.values(GAMES);
 export function gameMeta(id: GameId): GameMeta {
   return GAMES[id];
 }
+
+/**
+ * Meta for any lane, including one the reader invented (PRD F13).
+ *
+ * Pure, and total. Total matters: a lane id can outlive the game it names —
+ * an import can carry an event whose game did not come with it, and a reader
+ * can delete a game a stale render is still holding. Returning a neutral
+ * placeholder keeps that a visible oddity rather than a blank screen, which is
+ * the trade this codebase makes everywhere else in the client.
+ */
+export function metaFor(id: LaneId, custom: CustomGames): GameMeta {
+  const tracked = GAMES[id as GameId];
+  if (tracked !== undefined) return tracked;
+
+  const own = custom[id];
+  if (own !== undefined) {
+    return {
+      id: own.id as GameId,
+      name: own.name,
+      short: shortLabel(own.name),
+      hue: own.hue,
+      // Not credited in the colophon and contributing no standing chore: the
+      // colophon lists the sources we fetch, and this game has none. See
+      // docs/DATA-MODEL.md § Reader-authored key spaces.
+      studio: "",
+      dailyTasks: "",
+    };
+  }
+
+  return {
+    id: id as GameId,
+    name: "Unknown game",
+    short: "?",
+    hue: "#9AA3B8",
+    studio: "",
+    dailyTasks: "",
+  };
+}
+
+/** A name that still fits a narrow lane label or a chip. */
+export function shortLabel(name: string): string {
+  if (name.length <= 12) return name;
+  const first = name.split(/\s+/)[0] ?? name;
+  return first.length <= 12 ? first : `${name.slice(0, 11)}…`;
+}