feat(curl): add GET data aggregation

[subsetpark]

Summary

• Add curl -G/--get support so data options are appended to the query string.
• Preserve command-line order across repeated inline and file-backed data options.
• Match curl URL-encoding and default form content-type behavior.

Why

The current implementation overwrites repeated data flags and cannot move their payload to the URL. It also diverges from curl for spaces, percent-escape casing, and the default content type.

Validation

• 63 focused curl tests
• 3 live comparisons against system curl
• pnpm lint
• pnpm knip
• pnpm --filter just-bash typecheck
• pnpm --filter just-bash build
• Full test:run: 13,627 passed; one unrelated security hypothesis test was flaky in the combined run and passed on immediate isolated retry.

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