refactor(ts-migration): type src/api and the first of src/lib for noImplicitAny

Phase 12 step 1, in progress. The flag is not enabled yet — these are the
annotations it will require, landed first so the switch itself is a
one-line commit with a number that is already zero.

`noImplicitAny` projects 3496 errors across 242 files. This clears 179 of
them in 7 files: all of `src/api` (107 -> 0) and `workforce`,
`hiringRecords` in `src/lib`.

The leverage is real and worth recording, because it shapes the rest of
the step. Eight annotations on `aiEngine`'s prompt readers cleared 27
errors: where a value is `any`, every callback beneath it — `.map((c) =>
…)`, `.filter((r) => …)` — has no contextual type and errors on its own.
Typing the source fixes the callbacks for free, so this works bottom-up,
sources first.

Types are taken from what already exists wherever possible. The generated
entity types fit `workforce` and `hiringRecords` without a single
cascade: `JobPosting`, `JobApplication`, `Staff`, `AIInterview`,
`WorkerProfile`, `Assignment`, `Course`. `PreferencesUpdateResult` in
`src/types/user.ts` already described `updatePreferences`'s return.
`buildInsights` takes the other builders' outputs, so its parameters are
`ReturnType<typeof byDepartment>` and friends rather than a restatement
that could drift.

Two things are recorded rather than fixed:

`buildHires` probes four fields that are not `staff` columns —
`timeToHire`, `score`, `company` and `department` are absent from
`information_schema` and from the generated `Staff`. They are read as
fallbacks, so at run time they are always `undefined` and the other
branch always wins. `HireSourceRow` writes them down as optional so the
dead fallbacks are visible; removing the reads would be a behaviour
change. `Hire` likewise widens `profile_tier`, because the builder's
default `'skilled'` is lower-case where the column's check constraint
spells it `'Skilled'`.

`aiEngine`'s talent pool stays `any[]`. It is `JSON.parse` output from a
block embedded in a prompt, carrying computed fields like `match_score`
that no entity declares — typing it `WorkerProfile[]` would assert a
shape nothing validates.

One mistake worth keeping. I replaced an inline lookup with a hoisted
`const URGENCY = {…}`, and per-file esbuild said the output was
unchanged: with `--minify-syntax` it inlines a single-use const straight
back. The production bundle disagreed — `43e7f268` against `74d17e2d`.
Reverted to a type assertion, which erases. Hoisting reads as a tidy-up
and is a real change to the emitted code; the two checks disagreeing is
exactly why both are run.

  typecheck   0 under the committed config; 3317 under the probe, from 3496
  lint        exit 0
  npm test    1684/1691, the same 7 failures
  build       exit 0, bundle back to 74d17e2d…
  emitted JS  7/7 identical

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HBG1wnuRfJKCstGB8Fekr8

src/api/attendanceSeed.ts

@@ -39,15 +39,15 @@ const WINDOW_DAYS = 56;
  * Local rather than UTC because a shift belongs to the day it was worked in the
  * place it was worked, and `periodRange` windows on local day boundaries too.
  */
-function daysAgo(n, hour = 9, minute = 0, anchor = new Date()) {
+function daysAgo(n: number, hour = 9, minute = 0, anchor = new Date()) {
   const d = new Date(anchor.getTime());
   d.setDate(d.getDate() - n);
   d.setHours(hour, minute, 0, 0);
   return d;
 }
 
-const round1 = (n) => Math.round(n * 10) / 10;
-const round2 = (n) => Math.round(n * 100) / 100;
+const round1 = (n: number) => Math.round(n * 10) / 10;
+const round2 = (n: number) => Math.round(n * 100) / 100;
 const HOUR = 60 * 60 * 1000;
 
 /**
@@ -105,10 +105,21 @@ const ROSTER = [
  * Returning a plain record keeps every rule visible in one place instead of
  * spread across the generator.
  */
-const BEHAVIOUR = {
+/**
+ * One worker's shift outcome, as the rules below return it.
+ *
+ * `i` is the index of the shift counting back from the anchor, `weekday` the
+ * day it falls on. Rules that ignore the weekday take one argument, which is
+ * why the second is optional here.
+ */
+type ShiftBehaviour = (i: number, weekday?: number) => {
+  status: string; minutesLate: number; overtime: number; notes: string;
+};
+
+const BEHAVIOUR: Record<string, ShiftBehaviour> = {
   /* Reliable. One late arrival every couple of months, and overtime only on
      the nights events actually overrun. */
-  staff_marco: (i, weekday) => ({
+  staff_marco: (i: number, weekday?: number) => ({
     status: i === 14 ? 'late' : 'present',
     minutesLate: i === 14 ? 9 : 0,
     /* Friday and Saturday events overrun; midweek ones do not. */
@@ -124,7 +135,7 @@ const BEHAVIOUR = {
    * the six weeks before it — a change big enough to be worth surfacing and
    * specific enough to act on.
    */
-  staff_marcus: (i) => {
+  staff_marcus: (i: number) => {
     if (i === 2 || i === 7) {
       return { status: 'absent', minutesLate: 0, overtime: 0, notes: 'Called in sick' };
     }
@@ -145,7 +156,7 @@ const BEHAVIOUR = {
    * covers, on the three busiest shifts of each week. A steady climb rather
    * than a spike, which is exactly the shape that hides in a table of totals.
    */
-  staff_antoine: (i, weekday) => {
+  staff_antoine: (i: number, weekday?: number) => {
     const weekIndex = Math.floor(i / 5);
     const busy = weekday === 4 || weekday === 5 || weekday === 6;
     const overtime = busy ? Math.max(0.5, round1(3.5 - weekIndex * 0.45)) : 0;
@@ -154,8 +165,8 @@ const BEHAVIOUR = {
 };
 
 /** Every shift date for one worker, most recent first. */
-function shiftOffsets(weekdays, anchor) {
-  const offsets = [];
+function shiftOffsets(weekdays: number[], anchor: Date) {
+  const offsets: number[] = [];
   for (let offset = 0; offset <= WINDOW_DAYS; offset += 1) {
     const day = daysAgo(offset, 9, 0, anchor).getDay();
     if (weekdays.includes(day)) offsets.push(offset);
@@ -163,16 +174,16 @@ function shiftOffsets(weekdays, anchor) {
   return offsets;
 }
 
-const pad = (n) => String(n).padStart(2, '0');
-const localDate = (d) => `${d.getFullYear()}-${pad(d.getMonth() + 1)}-${pad(d.getDate())}`;
+const pad = (n: number) => String(n).padStart(2, '0');
+const localDate = (d: Date) => `${d.getFullYear()}-${pad(d.getMonth() + 1)}-${pad(d.getDate())}`;
 
 /**
  * @param {Date} [anchor] the day to count back from. Defaults to now, which is
  *   the point of this collection; a caller passes one only to hold the window
  *   still — see buildShiftsAt.
  */
-function buildShifts(anchor = new Date()) {
-  const records = [];
+function buildShifts(anchor: Date = new Date()) {
+  const records: any[] = [];
 
   for (const worker of ROSTER) {
     const offsets = shiftOffsets(worker.weekdays, anchor);
@@ -251,6 +262,6 @@ export const SHIFT_RECORDS = buildShifts();
  * shifts built around one day and bucketed around another describe two
  * different windows.
  */
-export function buildShiftsAt(anchor) {
+export function buildShiftsAt(anchor: Date) {
   return buildShifts(anchor);
 }