🐛 Stop QCO wire traversal at unknown carriers

[simon1hofmann]

🤖 AI text below 🤖

Description

Makes QCO wire traversal stop cleanly at an unknown SSA carrier instead of
terminating the process through reportFatalInternalError.

Unknown but verifier-accepted carrier operations are traversal boundaries: the
forward iterator reaches its sentinel, while backward traversal retains the
current qubit and reports no preceding operation. Known QCO wire operations keep
their existing behavior.

This is one focused replacement for draft PR #2287 and addresses part of #2255.

Validation

• new dynamic/static carrier regressions — 2/2 passed
• full QCO utilities suite — 138/138 passed
• uvx nox -s lint — passed
• git diff --check — passed

Checklist

• The pull request only contains commits that are focused and relevant to this change.
• I have added appropriate tests that cover the new/changed functionality.
• I have updated the documentation to reflect these changes.
• I have added entries to the changelog for any noteworthy additions, changes, fixes, or removals.
• I have added migration instructions to the upgrade guide (if needed).
• The changes follow the project's style guidelines and introduce no new warnings.
• The changes are fully tested and pass the CI checks.
• I have reviewed my own code changes.

If PR contains AI-assisted content:

• Any agent that created, edited, or submitted GitHub content was explicitly authorized for that scope, as required by our AI Usage Guidelines.
• Every agent-authored or agent-edited public text body begins with the visible disclosure 🤖 *AI text below* 🤖 (titles are exempt).
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• I confirm that I have personally reviewed and understood all AI-generated content, and accept full responsibility for it.

AI assistance disclosure: Codex extracted this focused change from the
authorized #2255 audit, validated it, and drafted this description.

[burgholzer]

Also reasonable 👍🏼

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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