✨ Add more inspection methods to QCProgram

[denialhaag]

Description

🤖 AI text below 🤖

Add gate_counts and static_depth inspection methods to QCProgram in C++ and Python. Gate counts group the existing static-IR gate metric by operation mnemonic.

Static depth follows qubit dependencies, takes the maximum across mutually exclusive SCF branches, visits each loop body once, and conservatively handles dynamic register indices. The methods share the existing modifier and barrier semantics and include C++ tests and Python documentation.

AI notice

This PR and its contents were created with the assistance of GPT-5.6 Sol via Codex.

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.

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[codecov]

Codecov Report

❌ Patch coverage is 92.23301% with 8 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
mlir/lib/Compiler/Programs.cpp	92.2%	8 Missing ⚠️

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