refactor: consolidate IPC types into src/shared/types.ts

The 12 cross-process data types were manually copied across
src/preload/index.ts and src/renderer/src/types/t4sd.d.ts. A silent
field addition or rename in either file would not produce a compile
error in the other — the divergence only surfaces at runtime.

A shared module makes the compiler enforce consistency. Preload imports
from shared/types and re-exports for downstream consumers. The renderer's
t4sd.d.ts re-exports the same types from shared/types, so all existing
screen imports continue to work without modification.

Both tsconfigs are extended to include src/shared so the module is
reachable from both composite projects.

tsconfig.node.json

@@ -20,6 +20,7 @@
     "src/main/**/*.ts",
     "src/main/**/*.d.ts",
     "src/preload/**/*.ts",
-    "src/preload/**/*.d.ts"
+    "src/preload/**/*.d.ts",
+    "src/shared/**/*.ts"
   ]
 }