fix: include migration files in @paperclipai/db and improve server error msg

- db build now copies src/migrations/ to dist/migrations/ after tsc,
  so SQL + meta JSON files are included in the published package.
  Without this, `import("@paperclipai/server")` fails at runtime with
  ENOENT when scanning for migration files.

- CLI's importServerEntry() now distinguishes between "module not found"
  and "server crashed during startup" for clearer error messages.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

cli/src/commands/run.ts

@@ -106,9 +106,15 @@ async function importServerEntry(): Promise<void> {
   try {
     await import("@paperclipai/server");
   } catch (err) {
+    if (isModuleNotFoundError(err)) {
+      throw new Error(
+        `Could not locate a Paperclip server entrypoint.\n` +
+          `Tried: ${devEntry}, @paperclipai/server\n` +
+          `${formatError(err)}`,
+      );
+    }
     throw new Error(
-      `Could not locate a Paperclip server entrypoint.\n` +
-        `Tried: ${devEntry}, @paperclipai/server\n` +
+      `Paperclip server failed to start.\n` +
         `${formatError(err)}`,
     );
   }