Add lightweight FASTQ file format support

[behroozazarkhalili]

Summary

This PR adds support for loading FASTQ files directly with load_dataset().

FASTQ is an extension of FASTA that includes quality scores for each base, widely used for storing output from high-throughput sequencing instruments.

Key Features

• Zero external dependencies - Pure Python parser based on readfq.py by Heng Li
• Quality score support - Preserves per-base quality scores as ASCII-encoded strings
• Streaming support - Generator-based parsing for memory efficiency with large NGS files
• Compression support - Automatic detection of gzip, bzip2, and xz compressed files
• Large sequence support - Uses large_string for both sequence and quality columns
• Parquet-safe batching - Dual-threshold batching (batch_size + max_batch_bytes) prevents page size errors

Columns

Column	Type	Description
id	string	Sequence identifier (first word after @)
description	string	Full description line (everything after id)
sequence	large_string	The nucleotide sequence
quality	large_string	ASCII-encoded quality scores (Phred+33 by default)

Supported Extensions

.fq, .fastq (and compressed variants: .fq.gz, .fastq.gz, .fq.bz2, .fq.xz)

Usage

from datasets import load_dataset

# Load FASTQ file
dataset = load_dataset("fastq", data_files="reads.fastq")

# Load gzipped file
dataset = load_dataset("fastq", data_files="reads.fq.gz")

# Filter columns
dataset = load_dataset("fastq", data_files="reads.fq", columns=["sequence", "quality"])

Quality Score Format

Quality scores use Sanger/Illumina 1.8+ encoding (Phred+33):

• ASCII character \! (33) = quality 0
• ASCII character I (73) = quality 40

Testing

• 22 comprehensive tests covering basic loading, multi-line sequences, compression, batching, schema types, and edge cases
• All tests passing
• Linting clean

References

• Follows pattern established in feat(fasta): add lightweight FASTA file format support #7923 (FASTA support)
• Parser based on: https://github.com/lh3/readfq
• Addresses feedback from Add fasta support #7851

cc: @georgia-hf