Page type-check: strict's flags that cost nothing, and catch variables as unknown (#235)

why(e) gives a caught error's message; each catch read e.message as any.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tsconfig.json

@@ -5,7 +5,13 @@
     "target": "es2022",
     "lib": ["es2022", "dom", "dom.iterable"],
     "noEmit": true,
+    // strict, a flag at a time (#235); noImplicitAny and strictNullChecks still to come.
     "strict": false,
+    "strictFunctionTypes": true,
+    "strictBindCallApply": true,
+    "noImplicitThis": true,
+    "alwaysStrict": true,
+    "useUnknownInCatchVariables": true,
     "skipLibCheck": true
   },
   "include": ["web/src/*.ts"]