Feature/Added depth calculation for branching statements

[vinayswamik]

Summary of changes

This PR addresses an issue in QasmVisitor where depth calculations for Gate and Measurement operations inside branching statements were being treated the same as non-conditional operations. As a result, both quantum and classical registers were not reflecting the correct depth, leading to inaccurate circuit-depth.

With this change, we introduce logic to:

• Detect when we are inside a branching statement (e.g., if or else): we set a flag at the start of QasmVisitor.
• Suspend immediate depth updates for all basic gates, custom gates, and measurements while inside the branch. Instead, we collect (and deduplicate) a set of all affected depth nodes (both quantum‐ and classical‐bit nodes) during the entire recursive traversal of that branch.
• Treat the entire branching block as a single depth increase.
• After exiting the branching block, take the maximum depth among all collected nodes and raise each one to “one step above” that maximum. In effect, this synchronizes every qubit and clbit participating in the conditional arguments to the correct final depth.

Closes #53

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[TheGupta2012]

Hey @vinayswamik , thanks for working on this! Giving a preliminary review right now, but the code looks good!

Please add some more tests whenever you get time

[vinayswamik]

Hey @vinayswamik , thanks for working on this! Giving a preliminary review right now, but the code looks good!

Please add some more tests whenever you get time

Thanks for the review 👍,
Sure I will add few more test cases and lyk

[TheGupta2012]

Changes lgtm @vinayswamik ! Can you please also add a CHANGELOG.md entry ? It will be good if you can specify an example program there. Post that, we can merge.

Thanks for working on this!

[vinayswamik]

Changes lgtm @vinayswamik ! Can you please also add a CHANGELOG.md entry ? It will be good if you can specify an example program there. Post that, we can merge.

Thanks for working on this!

Thanks for your support @TheGupta2012. I have update the CHANGELOG.md and added one new test case to cover external gate depth inside branching statements. Let me know if any changes are needed.

[TheGupta2012]

Good to merge