New structured error types

Three new error classes are introduced for cleaner error handling and telemetry:

• RipgrepNullByteError: thrown when ripgrep is called with a null byte in its arguments
• RipgrepUsageError: thrown when ripgrep rejects the pattern, glob, or file type filter without searching (previously these were untyped failures)
• SelectedRangeTooLargeError: thrown when a requested line range exceeds the readable limit; the error message now names the limit and suggests searching for specific content instead
• BedrockUnexpectedContentTypeError: thrown when a Bedrock streaming response has an unexpected content-type (not application/vnd.amazon.eventstream); includes guidance to set CLAUDE_CODE_DISABLE_BEDROCK_CONTENT_TYPE_GUARD=1 to suppress while a gateway is being fixed