fix(runtime): honor the starting offset when paginating

[git-jxj]

Summary

Offset pagination with --all sends the requested starting offset on the first page, but resets its counter to zero afterward. For --offset 2 --limit 2, the requests use offsets 2, 2, 4, 5 and duplicate the first fetched page.

Initialize the counter from the resolved request query so both explicit offsets and specification defaults continue from the requested page. Regression tests exercise the generated command runtime against HTTP fixtures, including custom and encoded parameter names, different page sizes, total metadata, and an empty first page.

Verification

• make check
• go test -race ./...
• go build ./...

The new regressions fail against the original implementation and pass with this change.

Compatibility

Offset-based --all now advances from the starting offset already sent in the first request. The CLI usage documentation describes this behavior.

Checklist

• Tests or focused verification cover the changed surface.
• User-facing behavior changes are documented.
• Generated output under internal/generated/, .cache/, and ad-hoc skills/<cli-name>/ directories is not committed.
• Commits are signed off when this is ready to merge.

[samzong]

@git-jxj Thank you for your attention.