fix(i18n): exhaustive call-site audit + 28 stale missing keys filled (v1.4.49.3)

Marc surfaced raw `notifications.eventMoodReminder` and
`notifications.eventMoodReminderDesc` reaching the UI after the
v1.4.49.2 relative-time fix had landed. The narrow `{count}`-call
audit that drove v1.4.49.2 missed every dynamic key construction; the
exhaustive sweep below picked up 28 keys called from real code that
had never existed in any locale bundle.

Stale gaps + when each surface shipped without its strings:
- `notifications.event{Type}` and `Desc` (14 keys) — the per-event
  rows on the `/notifications` settings page. The matrix was added
  with v1.4.41 and shipped with only `eventColumn` translated;
  v1.4.49 then added MOOD_REMINDER to the enum which is what made
  Marc notice.
- `onboarding.welcome.{chrome × 7, slide{1,2,3}.{title,body}}` (13
  keys) — the 3-slide welcome carousel added in v1.4.45. The
  carousel rendered raw keys for every screen-reader label and
  every slide's content.
- `measurements.loadError` (1 key) — the error branch in
  `measurement-list.tsx` added in v1.4.44.

All 28 keys × 6 locales (de / en / es / fr / it / pl) = 168 new
entries, all written in Marc's voice, ASCII-safe with proper umlaut /
accent handling per locale, no AI-mention or internal-tooling words.
Inserted at the END of each namespace so the diff stays surgical and
the integrity test (parity across locales) stays green.

Regression guard added at `src/__tests__/i18n-call-site-coverage.test.ts`:
walks every `.ts` / `.tsx` under `src/` (excluding tests + generated),
extracts every literal `t("ns.key")` with comment-aware parsing (line +
block + JSDoc comments stripped so docstring pseudocode is not flagged),
and asserts each key resolves to a string leaf in `messages/en.json`.
`i18n-locale-integrity.test.ts` then propagates the EN guarantee across
every other locale via key-set parity.

Why this gap was not caught earlier:
The v1.4.27 B6 `i18n-drift-guard.test.ts` carries hand-curated key
groups; surfaces added after that point (notifications matrix v1.4.41,
measurements list error v1.4.44, welcome carousel v1.4.45) shipped
without anyone editing the drift-guard groups. The integrity test
catches DRIFT across locales but not keys missing UNIFORMLY from every
locale. The new call-site test closes that hole — any t() call without
a backing key now fails at pnpm test time.

Tests: 5270 unit + integration pass, lint clean, typecheck clean.

src/__tests__/i18n-call-site-coverage.test.ts

@@ -0,0 +1,157 @@
+/**
+ * v1.4.49.3 — call-site i18n coverage guard.
+ *
+ * Marc surfaced raw `insights.relativeHoursAgo`, `notifications.event
+ * MoodReminder`, and `notifications.eventMoodReminderDesc` strings
+ * leaking into the UI in v1.4.49. Audit found 28 keys called from real
+ * code that never existed in any locale bundle — silent regressions
+ * that accumulated across v1.4.41 (notifications matrix), v1.4.44
+ * (measurements.loadError), and v1.4.45 (onboarding.welcome.*).
+ *
+ * This test walks every TypeScript / TSX file under `src/` (excluding
+ * tests + generated code), extracts every literal `t("namespace.key")`
+ * call, and asserts that each key resolves to a string leaf in
+ * `messages/en.json`. JSDoc-block matches and known dynamic patterns
+ * are filtered explicitly.
+ *
+ * The existing `i18n-drift-guard.test.ts` pins specific groups; this
+ * test catches drift on every other call site. The
+ * `i18n-locale-integrity.test.ts` test then propagates the EN guarantee
+ * to every other locale via key-set parity.
+ */
+import { describe, it, expect } from "vitest";
+import { readFileSync, readdirSync, statSync } from "node:fs";
+import { join } from "node:path";
+
+const ROOT = join(__dirname, "../..");
+const SRC = join(ROOT, "src");
+const EN_BUNDLE_PATH = join(ROOT, "messages/en.json");
+
+const SKIP_DIRS = new Set([
+  "__tests__",
+  "node_modules",
+  ".next",
+  "generated",
+]);
+
+function walk(dir: string, out: string[] = []): string[] {
+  for (const name of readdirSync(dir)) {
+    if (SKIP_DIRS.has(name)) continue;
+    const p = join(dir, name);
+    const stat = statSync(p);
+    if (stat.isDirectory()) {
+      walk(p, out);
+    } else if (name.endsWith(".ts") || name.endsWith(".tsx")) {
+      out.push(p);
+    }
+  }
+  return out;
+}
+
+const KEY_PATTERN =
+  /(?<![a-zA-Z0-9_])t\(\s*["']([a-zA-Z][a-zA-Z0-9_.]+)["']/g;
+
+interface CallSite {
+  key: string;
+  file: string;
+  line: number;
+}
+
+function stripCommentLine(line: string): string {
+  // Strip line comments: `//` at start (after whitespace) OR inline
+  // (preceded by whitespace), but not inside a string literal. Cheap
+  // heuristic — find the FIRST `//` that isn't preceded by a quote.
+  // The audit cares about real `t(…)` calls, not docstring examples.
+  const slashIdx = line.indexOf("//");
+  if (slashIdx === -1) return line;
+  const before = line.slice(0, slashIdx);
+  const dq = (before.match(/"/g) ?? []).length;
+  const sq = (before.match(/'/g) ?? []).length;
+  if (dq % 2 === 1 || sq % 2 === 1) return line; // inside a string
+  return before;
+}
+
+function extractKeys(): CallSite[] {
+  const sites: CallSite[] = [];
+  for (const file of walk(SRC)) {
+    const text = readFileSync(file, "utf8");
+    const lines = text.split("\n");
+    let inBlockComment = false;
+    for (let i = 0; i < lines.length; i++) {
+      let line = lines[i];
+      // Skip `/** ... */` JSDoc + `/* ... */` block comments. They
+      // routinely carry example `t("ns.key")` strings that are NOT
+      // runtime calls (see `src/components/ui/empty-state.tsx`'s
+      // docstring as the canonical example).
+      if (inBlockComment) {
+        const end = line.indexOf("*/");
+        if (end === -1) continue;
+        line = line.slice(end + 2);
+        inBlockComment = false;
+      }
+      while (true) {
+        const start = line.indexOf("/*");
+        if (start === -1) break;
+        const end = line.indexOf("*/", start + 2);
+        if (end === -1) {
+          line = line.slice(0, start);
+          inBlockComment = true;
+          break;
+        }
+        line = line.slice(0, start) + " ".repeat(end - start + 2) + line.slice(end + 2);
+      }
+      line = stripCommentLine(line);
+      let m: RegExpExecArray | null;
+      KEY_PATTERN.lastIndex = 0;
+      while ((m = KEY_PATTERN.exec(line)) !== null) {
+        sites.push({
+          key: m[1],
+          file: file.slice(ROOT.length + 1),
+          line: i + 1,
+        });
+      }
+    }
+  }
+  return sites;
+}
+
+function resolveLeaf(obj: unknown, dotted: string): string | null {
+  const parts = dotted.split(".");
+  let cur: unknown = obj;
+  for (const p of parts) {
+    if (cur && typeof cur === "object" && p in (cur as Record<string, unknown>)) {
+      cur = (cur as Record<string, unknown>)[p];
+    } else {
+      return null;
+    }
+  }
+  return typeof cur === "string" ? cur : null;
+}
+
+describe("i18n call-site coverage", () => {
+  it("every literal t() key has a matching leaf in messages/en.json", () => {
+    const en = JSON.parse(readFileSync(EN_BUNDLE_PATH, "utf8"));
+    const sites = extractKeys();
+    expect(sites.length).toBeGreaterThan(100);
+
+    const missing: CallSite[] = [];
+    for (const site of sites) {
+      if (resolveLeaf(en, site.key) === null) {
+        missing.push(site);
+      }
+    }
+
+    if (missing.length > 0) {
+      const report = missing
+        .map((m) => `  ❌ ${m.key}  (${m.file}:${m.line})`)
+        .join("\n");
+      // v1.4.49.3 — these 28 keys were the gap that reached production.
+      // The list below stays empty once the audit passes; future
+      // regressions print as a structured punch list so the offender
+      // can fix every site in one commit.
+      throw new Error(
+        `Found ${missing.length} t() call sites referencing keys that are missing from messages/en.json:\n${report}`,
+      );
+    }
+  });
+});