VQkit v1.1 — Quantum ESPRESSO mechanical analysis fix

Problem
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Mechanical Properties option [2] could fail to read valid QE pw.x outputs.

Cause
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The QE stress parser expected the literal header text 'total stress'.
Quantum ESPRESSO commonly prints variable spacing, for example:

    total   stress  (Ry/bohr**3)  (kbar)

Fix
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The parser now accepts arbitrary whitespace between 'total' and 'stress'.

Validation
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Verified against the supplied QE stress-strain workflow:
- 6 independent strain modes
- 4 strain values per mode
- 24 QE calculations
- no missing calculations
- full 6 x 6 stiffness tensor reconstructed
- VRH/mechanical properties calculated
