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.

bin/gstack-gbrain-sync.ts

@@ -75,7 +75,10 @@ interface CodeStageDetail {
     | "failed"
     | "refused-autopilot"
     | "refused-reclone"
-    | "refused-egress-receipt";
+    | "refused-egress-receipt"
+    | "skipped-policy-read-only"
+    | "refused-policy-deny"
+    | "refused-policy-unreadable";
 }
 
 interface StageResult {