Remove pinned cudaq_realtime_version

[anjbur]

Description

• Remove .cudaq_realtime_version in favor of .cudaq_version
• Add logging to indicate the chosen CUDA-Q version in the get-cudaq-version action

Test run of All libs (Release) workflow: https://github.com/NVIDIA/cudaqx/actions/runs/26310275121

Runtime / performance impact

Self-review checklist

Please confirm each item before requesting review. Check [x] or strike
through and explain.

Before requesting review

• I reviewed my own full diff in GitHub or my editor.
• PR is in Draft if it is not yet ready for review.
• Temporary / debugging changes have been removed.
• Local test logs reviewed; no unexplained warnings or errors.
• CI logs reviewed; no unexplained warnings or errors.
• Full CI has been run.

Scope and size

• PR is under ~1000 lines, or an exception is justified in the description.
• Refactoring-only changes are isolated in their own PR(s).
• No existing tests were disabled or modified just to make this PR pass
  (if so, an issue has been raised).

Tests

• New functionality has new tests.
• Tests fail if the new functionality is broken (including crashes), not
  just when it is missing.
• Negative tests added where exceptions are expected.
• Truth data added where simple EXPECT_* / assert checks are
  insufficient for algorithmic correctness.
• CI runtime impact considered; team notified if significant.

Documentation

• Public-facing APIs have Doxygen docs.
• User-visible behavior changes have public docs, or a follow-up is
  tracked.
• User-facing docs for new features are in a separate PR held until
  release (the docs site publishes immediately on merge to the default
  branch, so feature docs must not land before the feature ships).

Code style

• Naming follows the existing convention (snake_case vs camelCase) for
  the area being modified.

Dependencies

• No new third-party dependencies, or the team has been notified and
  OSRB tickets filed.

[anjbur]

Testing blocked by broken All libs (Release) pipeline. See #562 for debugging and eventual fix.

[anjbur]

Moving back to draft to block merge until parallel changes are ready on GitLab.