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.web.json

@@ -17,5 +17,9 @@
     "resolveJsonModule": true,
     "allowSyntheticDefaultImports": true
   },
-  "include": ["src/renderer/**/*.ts", "src/renderer/**/*.tsx"]
+  "include": [
+    "src/renderer/**/*.ts",
+    "src/renderer/**/*.tsx",
+    "src/shared/**/*.ts"
+  ]
 }