Function loadConfig

loadConfig(): B2Config
Load and validate configuration from environment variables.

Returns B2Config
The validated B2 server configuration.
Remarks
This is the stdio bootstrap path. It intentionally exits the process on invalid credential configuration because stdio hosts expect startup failures to be reported on stderr instead of returned as MCP tool results.

Throws
Error when a non-credential startup failure escapes configuration loading.
Example
```
const config = loadConfig();
const server = createServer(config, await fetchCapabilities(config));
```
- Defined in server.ts:111