feat: require a zero-error product typecheck and a test type-debt ratchet

Adds tsconfig.json (strict) over product code, fixes its remaining 90
diagnostics (type-only, interface corrections, and explicit narrowing),
and adds a typecheck job to the required free-tests aggregate running
bun run typecheck, the test-code ratchet (identity -> count baseline, fails
on new, repeated, or unlocked fixed diagnostics), and the lib/cso format
check. Reuses fixes from #2447 where they still applied.

scripts/psychographic-signals.ts

@@ -36,7 +36,7 @@
  *   architecture_care:  0 = pragmatic, ship it      ↔  1 = principled, get it right
  */
 
-import { QUESTIONS } from './question-registry';
+import { QUESTIONS, type QuestionDef } from './question-registry';
 
 /** The 5 dimensions of the developer psychographic. */
 export type Dimension =
@@ -255,7 +255,7 @@ export function validateRegistrySignalKeys(): {
   extra: string[];
 } {
   const registrySignalKeys = new Set<string>();
-  for (const q of Object.values(QUESTIONS)) {
+  for (const q of Object.values(QUESTIONS) as QuestionDef[]) {
     if (q.signal_key) registrySignalKeys.add(q.signal_key);
   }
   const mapKeys = new Set(Object.keys(SIGNAL_MAP));