feat: add concat command to concatenate multiple WARC files

[NGTmeaty]

No description provided.

[Copilot]

Pull request overview

Adds a new warc concat subcommand to combine multiple WARC files into a single output file, with optional deletion of the original inputs.

Changes:

• Register a new concat Cobra subcommand in the warc CLI.
• Implement byte-level concatenation of multiple input files into a single output file.
• Add a safety check to refuse concatenation of gowarc zstd dictionary-frame files.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 5 comments.

File	Description
cmd/warc/main.go	Registers the new concat subcommand on the root CLI.
cmd/warc/concat/concat.go	Implements concatenation, logging, dictionary-frame detection, and optional input deletion.

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[yzqzss]

IIRC, WARC Spec allows you to directly concat multiple warc files without rewriting the warc records? (cat *.warc > one.warc)

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

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[willmhowes]

IIRC, WARC Spec allows you to directly concat multiple warc files without rewriting the warc records? (cat *.warc > one.warc)

@yzqzss Yes! We just wanted a convenient way to accomplish WARC concatenation within existing toolset

[NGTmeaty]

Changes look good to me!