fix(editor): remove stale items after rewrite

[pablopupo]

Fixes #45.

rewrite_content only replaced refs[0], leaving the other selected items behind. The selected refs are now deduplicated and put in document order before the replacement, and the remaining originals are removed afterward.

Added regression coverage for multiple refs, duplicate refs, and nested items.

[github-actions]

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[mergify]

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🟢 Enforce conventional commit

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• title ~= ^(fix|feat|docs|style|refactor|perf|test|build|ci|chore|revert)(?:\(.+\))?(!)?: