[NiranjanRSoorej06]

Summary

Validate state vector shapes before checking qubit map indices in PauliSum.expectation_from_state_vector.

Add regression tests for invalid state vector sizes and ensure existing qubit map validation behavior is preserved.

Tests

• linear_combinations_test.py: 224 passed
• pauli_string_test.py: 420 passed
• Formatting, lint, and changed-file checks passed.
• Confirmed that the regression test fails on the original implementation and passes with this change.

Screenshots

1. Baseline: Regression Test Fails on Original Implementation

2. Baseline Test Output: Incorrect Validation Error 3. Regression Failure: Expected Shape Validation Error 4. Fixed Implementation: Regression Tests Pass

The full test suite had 3 failures related to missing LaTeX tooling in the local environment.

Fixes #8463