feat(illness): add the condition-journal MVP behind a born-gated module

Introduce a retrospective illness/condition journal: episodes with a
lifecycle (acute / chronic-ongoing / recurring / flare) and a daily
symptom timeline forked structurally from the cycle log-day surface. The
journal is a record, not a medical device — no prediction or diagnosis UI.

- Register `illness` as a born-gated (opt-in / default-off) module. The
  gate resolver flips the disabled-allowlist default to off for born-gated
  keys, so the surface stays dark until the account opts in from the
  Modules hub. `isIllnessEnabled` + `requireIllnessEnabled` delegate to the
  module foundation (one source of truth) and re-stamp an illness errorCode.
- Episode CRUD under /api/illness: list / create / get / edit / resolve /
  delete, plus a per-episode-day day-log upsert on (episodeId, date). Every
  route wraps apiHandler, Zod-validates with returnAllZodIssues, narrows
  userId from auth, builds data field-by-field, and gates the module.
  Free-text notes encrypt at rest through the shared Bytes codec.
- Log-day sheet (cycle fork): ~8 Jackson/WURSS symptom chips 0-3 + a
  functional-impact group + fever + an encrypted note, one row per day.
- Episode history page + a born-gated nav entry, neutral palette, status
  via a neutral Badge, retrospective-only copy. i18n across all six locales.
- Cover the new routes in the module-route-gate inventory; unit tests for
  the day-log upsert, the gate enforcement, and the born-gated resolver.

The /api/auth/me module map now projects the `illness` flag (openapi.yaml
regenerated).

src/lib/modules/__tests__/gate.test.ts

@@ -78,6 +78,54 @@ describe("resolveModuleEnabled — disabled allowlist (default-on)", () => {
   });
 });
 
+describe("resolveModuleEnabled — born-gated module (illness, default-off)", () => {
+  it("is OFF when no preference is recorded (opt-in, not default-on)", () => {
+    expect(resolveModuleEnabled("illness", inputs(), true, ALL_AVAILABLE)).toBe(
+      false,
+    );
+  });
+
+  it("is ON only on an explicit true", () => {
+    expect(
+      resolveModuleEnabled(
+        "illness",
+        inputs({ modulePreferences: { illness: true } }),
+        true,
+        ALL_AVAILABLE,
+      ),
+    ).toBe(true);
+  });
+
+  it("stays OFF on an explicit false", () => {
+    expect(
+      resolveModuleEnabled(
+        "illness",
+        inputs({ modulePreferences: { illness: false } }),
+        true,
+        ALL_AVAILABLE,
+      ),
+    ).toBe(false);
+  });
+
+  it("operator-off short-circuits even when the user opted in", () => {
+    expect(
+      resolveModuleEnabled(
+        "illness",
+        inputs({ modulePreferences: { illness: true } }),
+        true,
+        operator({ illness: false }),
+      ),
+    ).toBe(false);
+  });
+
+  it("does not affect sibling default-on modules", () => {
+    const i = inputs({ modulePreferences: {} });
+    expect(resolveModuleEnabled("illness", i, true, ALL_AVAILABLE)).toBe(false);
+    expect(resolveModuleEnabled("mood", i, true, ALL_AVAILABLE)).toBe(true);
+    expect(resolveModuleEnabled("labs", i, true, ALL_AVAILABLE)).toBe(true);
+  });
+});
+
 describe("resolveModuleEnabled — cycle delegation", () => {
   it("ignores the module blob and reads the cycle gate (gender-derived)", () => {
     // Even a crafted `{ cycle: false }` blob cannot override the real

src/lib/modules/gate.ts

@@ -55,6 +55,7 @@ import {
 } from "./operator-availability";
 import {
   MODULE_KEYS,
+  isBornGatedModule,
   moduleDelegatesTo,
   type ModuleKey,
 } from "./registry";
@@ -146,6 +147,13 @@ export function resolveModuleEnabled(
     return assistantCoach && !inputs.disableCoach;
   }
 
+  if (isBornGatedModule(key)) {
+    // BORN-GATED (opt-in / default-off): inverse of the disabled allowlist.
+    // The module stays OFF until the account explicitly enables it — only a
+    // literal `true` turns it on, so the surface never appears unbidden.
+    return inputs.modulePreferences[key] === true;
+  }
+
   // Disabled allowlist: only an explicit `false` turns the module off.
   return inputs.modulePreferences[key] !== false;
 }

src/lib/modules/registry.ts

@@ -72,6 +72,17 @@ export interface ModuleDefinition {
    * link; `labelKey` names the destination ("Account", "Coach settings").
    */
   managedAt?: { href: string; labelKey: string };
+  /**
+   * v1.18.1 — BORN-GATED (opt-in / default-off). A born-gated module is
+   * the inverse of the standard disabled-allowlist: it stays OFF until the
+   * account explicitly enables it (`modulePreferencesJson[key] === true`).
+   * Used for new optional verticals (the illness/condition journal) that
+   * ship dark and only appear once the user opts in from the Modules hub.
+   * The gate's `false`-disables contract still holds — an explicit `false`
+   * (or simply the absent default) keeps it off — but here ONLY an explicit
+   * `true` turns it on, so the surface never appears unbidden.
+   */
+  bornGated?: boolean;
 }
 
 /**
@@ -88,6 +99,7 @@ export const MODULE_KEYS = [
   "workouts",
   "recovery",
   "labs",
+  "illness",
   "achievements",
   "coach",
   "insights",
@@ -169,6 +181,15 @@ export const MODULE_REGISTRY: Readonly<Record<ModuleKey, ModuleDefinition>> =
       descriptionKey: "modules.labs.description",
       category: "tracking",
     },
+    illness: {
+      key: "illness",
+      labelKey: "modules.illness.label",
+      descriptionKey: "modules.illness.description",
+      category: "tracking",
+      // Ships dark — only appears once the account opts in from the
+      // Modules hub. Default-off, no nag, retrospective-only.
+      bornGated: true,
+    },
     sleep: {
       key: "sleep",
       labelKey: "modules.sleep.label",
@@ -230,3 +251,12 @@ export function isModuleKey(key: string): key is ModuleKey {
 export function moduleDelegatesTo(key: ModuleKey): ModuleDelegation | undefined {
   return MODULE_REGISTRY[key].delegatesTo;
 }
+
+/**
+ * v1.18.1 — true for a born-gated (opt-in / default-off) module. The gate
+ * flips its default from on to off for these keys: they require an explicit
+ * `modulePreferencesJson[key] === true` to enable.
+ */
+export function isBornGatedModule(key: ModuleKey): boolean {
+  return MODULE_REGISTRY[key].bornGated === true;
+}